Spector et al. Vol. 14, No. 3 /March 1997/J. Opt. Soc. Am. B 511

Analysis of the third spectrum of dysprosium(Dy III)

Nissan Spector

Soreq Nuclear Research Center, Yavne 81800, Israel

Jack Sugar

National Institute of Standards and Technology, Gaithersburg, Maryland 20899-0001

Jean-Francois Wyart

Centre National de la Recherche Scientifique, Campus D’Orsay, 91405 Orsay Cedex, France

Received July 9, 1996

The third spectrum of dysprosium has been observed in a sliding-spark discharge with a 10.7-m normal-incidence spectrograph in the wavelength region between 2007 and 5020 Å. Of the 2500 lines that were at-tributed to Dy III, 544 are classified. With these data 106 energy levels were established, including five of the5I ground term of the 4f10 configuration, 49 of 4f 95d, 15 of 4f 96s, and 37 of 4f 96p. The levels have beeninterpreted theoretically and have been assigned percentage compositions in the most appropriate couplingschemes. Using semiempirical calculations with least-squares-fitted radial parameters, we have obtained av-erage deviations between experimental and calculated levels of 649, 629, and 616 cm21 for the 4f 95d, the4f 96p, and the 4f 96s configurations, respectively. The overlapping configurations 4f 95d and 4f 96s showslight evidence of configuration interaction. This analysis leaves Pm III as the last spectrum of a doubly ion-ized rare earth to remain uninterpreted. With these data, a value of 184 970 6 800 cm21 has been derived forthe ionization energy. © 1997 Optical Society of America [S0740-3224(97)02203-0]

1. INTRODUCTIONOf all the third spectra of the rare-earth elements, exceptfor Pm, that of Dy III alone has resisted interpretation. Alikely reason is that most of the 4f–5d resonance transi-tions are weak because the low terms of the 4f 95d con-figuration are septets, whereas there are no septets in the4f10 ground configuration of Dy III. The first levels of4f 95d found from combinations with the low terms of4f 96p were septets. Thus progress in the analysis wasdelayed by the need to work with weak, intersystem lines.The key to success in the analysis was the combination

of accurately measured wavelengths and accurate predic-tions of the energy levels. We measured 2500 lines, de-termined experimentally to belong to Dy III, in the wave-length range of 2007–5020 Å with a 1s uncertainty of60.003 Å. From theoretical analyses of other third spec-tra of the rare earths we were able to interpolate accuratevalues for the radial integrals to use in calculating thelevels. J.-F. Wyart, working independently, found the4f10 5I term intervals by using a limited line list andscaled values of the 4f106s2 5I ground term intervals ofDy I. At the same time, the first two authors located lowlevels of the other three configurations. The connectionof the two systems of levels was made through weak in-tersystem lines present in the extended line list. The re-sulting 106 energy levels allowed approximately 600 linesto be classified, accounting for approximately 70% of theintensity of the spectrum.

0740-3224/97/030511-11$10.00 ©

2. EXPERIMENTAL DETAILSThe spectra were photographed at the National Instituteof Standards and Technology with the 10.7-m normal-incidence spectrograph having a grating with 1200grooves/mm. The Dy III spectrum was well developedin a sliding-spark discharge1 operating at 50-A peakcurrent. Lines of Dy II and Dy IV are stronger in 6-and 500-A sliding-spark discharges, respectively. Theexposure times were adjusted to emphasize this distinc-tion. By comparison of spectra made with these threespark conditions a list of purely Dy III lines was obtained.For wavelength standards internal impurity lines ofC, N, O, Si, and Al as well as external hollow cathodespectra of Ar, Fe, Cu, and Ge were used for wavelengthcalibration2 and for detecting shifts between the Dyspectra and the external calibration lines throughcommon impurities. The wavelength uncertainty isestimated to be 60.005 Å. The level values wereoptimized by means of the computer program ELCALC.3

A list of lines (wavelengths in air) classified inthe present analysis is given in Table 1. The inten-sity values are visual estimates of relative plate blacken-ing. The classifications are represented by the valuesof the energy levels involved in the transition, givento the units place, with the J values given as sub-scripts and odd parity shown by superscript o. Thereare 616 classified lines, eleven of which are doubly classi-fied.

1997 Optical Society of America

512 J. Opt. Soc. Am. B/Vol. 14, No. 3 /March 1997 Spector et al.

Table 1. Classified lines of Dy III

Wavelengtha Wave number Wavelengtha Wave number(Å) Intensity (cm21) Classification (Å) Intensity (cm21) Classification

2007.326 1 49 801.41 72 5244–22 7224+

2030.655 10 49 229.35 68 4115–19 1826+

2036.119 100 49 097.26 70 2714–21 1745+

2042.042 6 48 954.88 72 6656–23 7105+

2058.634 150 48 560.36 65 0137–16 4538+

2060.731 1 48 510.95 72 6656–24 1547+

2065.005 1 48 410.56 67 5935–19 1826+

2067.430 1000 48 353.79 64 8079–16 4538+

2071.730 8 48 253.44 72 9646–24 7106+

2077.194 2 48 126.52 74 0365–25 9104+

2078.985 100 48 085.07 65 5316–17 4467+

2084.351 1000 47 961.29 64 4148–16 4538+

2091.596 4 47 795.19 66 9775–19 1826+

2095.297 6 47 710.77 70 4333–22 7224+

2097.980 3 47 649.77 72 0827–24 4328+

2099.642 2 47 612.05 73 7244–26 1125+

2102.435 10 47 548.81 70 2714–22 7224+

2105.693 10 47 475.25 72 1865–24 7106+

2110.887 10 47 358.45 68 5336–21 1745+

2113.204 1 47 306.53 68 4814–21 1745+

2115.796 20 47 248.58 68 4115–21 1636+

2116.306 8 47 237.20 68 4115–21 1745+

2119.150 1 47 173.81 73 0835–25 9104+

2126.074 6 47 020.20 66 2026–19 1826+

2128.428 20 46 968.20 64 4148–17 4467+

2144.511 1 46 616.00 67 7796–21 1636+

2144.595 100 46 614.17 72 5244–25 9104+

2144.976 10 46 605.89 73 0835–26 4776+

2148.690 1500 46 525.34 68 3878–21 8618+

2153.117 1 46 429.70 67 5935–21 1636+

2153.945 4 46 411.84 72 5244–26 1125+

2164.386 10 46 187.98 72 6656–26 4776+

2165.893 10 46 155.84 70 8667–24 7106+

2168.788 800 46 094.24 70 2496–24 1547+

2171.556 10 46 035.49 70 7465–24 7106+

2173.635 1000 45 991.47 67 8537–21 8618+

2174.720 20 45 968.52 73 0835–27 1156+

2176.257 100 45 936.06 68 3878–22 4517+

2178.506 100 45 888.64 63 3347–17 4467+

2181.243 10 45 831.07 65 0137–19 1826+

2181.839 20 45 818.55 71 9304–26 1125+

2182.576 20 45 803.08 66 9775–21 1745+

2187.099 30 45 708.37 72 1865–26 4776+

2198.591 1 45 469.47 73 7146–28 2447+

2199.249 3 45 455.88 74 3894–28 9345+

2201.866 40 45 401.86 67 8537–22 4517+

2203.278 80 45 372.76 62 8196–17 4467+

2204.516 40 45 347.28 72 6656–27 3185+

2211.424 10 45 205.64 72 5244–27 3185+

2214.470 8 45 143.47 69 8545–24 7106+

2214.846 6000 45 135.81 64 8079–19 6719+

2216.477 4 45 102.59 74 0365–28 9345+

2220.147 80 45028.05 66 2026–21 1745+

2222.093 60 44 988.61 74 3894–29 4015+

2227.956 60 44 870.24 67 5935–22 7224+

2229.648 50 44 836.19 70 7465–25 9104+

(Table continued)

2230.349 80 44 822.10 68 5336–23 7105+

2234.286 2000 44 743.13 644148–19 6719+

2236.005 1 44 708.74 73 7146–29 0057+

2239.744 2 44 634.11 70 7465–26 1125+

2240.843 1 44 612.22 71 9304–27 3185+

2245.410 2 44 521.49 72 9646–28 4426+

2252.661 2000 44 378.20 68 5336–24 1547+

2253.178 20 44 368.01 65 5316–21 1636+

2253.750 40 44 356.75 65 5316–21 1745+

2257.467 5000 44 283.72 67 0064–22 7224+

2258.245 250 44 268.47 70 7465–26 4776+

2260.562 100 44 223.10 72 6656–28 4426+

2261.924 200 44 196.47 68 3878–24 1909+

2263.789 1 44 160.06 70 8667–26 7067+

2263.805 3 44 159.75 70 2714–26 1125+

2264.181 1000 44 152.42 63 3347–19 1826+

2264.311 6 44 149.89 73 0835–28 9345+

2268.488 60 44 068.60 67 7796–23 7105+

2269.210 2 44 054.58 72 9646–28 9096+

2270.207 100 44 035.23 70 8667–26 8318+

2272.462 1 43 991.54 65 1545–21 1636+

2273.049 4000 43 980.18 65 1545–21 1745+

2279.788 4000 43 850.19 65 0137–21 1636+

2280.426 2 43 837.92 72 0827–28 2447+

2281.239 25 43 822.30 68 5336–24 7106+

2283.900 200 43 771.25 70 2496–26 4776+

2284.682 1 43 756.27 72 6656–28 9096+

2287.569 30 43 701.05 68 4115–24 7106+

2287.707 1500 43 698.41 67 8537–24 1547+

2287.908 30 43 694.58 72 9646–29 2696+

2288.538 40 43 682.55 73 0835–29 4015+

2290.950 4000 43 636.56 62 8196–19 1826+

2291.245 10 43 630.94 70 7465–27 1156+

2291.579 800 43 624.58 67 7796–24 1547+

2293.391 20 43 590.11 72 5244–28 9345+

2293.829 80 43 581.80 73 7146–30 1326+

2301.969 10 43 427.70 70 7465–27 3185+

2302.147 40 43 424.34 74 3894–30 9654+

2304.681 2 43 376.60 69 8545–26 4776+

2310.534 250 43 266.73 66 9775–23 7105+

2311.322 10 43 251.98 72 1865–28 9345+

2312.571 6000 43 228.63 59 6818–16 4538+

2316.694 2500 43 151.70 65 0137–21 8618+

2320.697 1000 43 077.27 72 0827–29 0057+

2323.936 5000 43 017.23 59 4707–16 4538+

2327.381 250 42 953.56 68 3878–25 4338+

2329.391 10 42 916.50 72 1865–29 2696+

2337.021 10 42 776.40 70 8667–28 0907+

2337.978 3 42 758.89 73 7244–30 9654+

2339.098 60 42 738.43 68 5336–25 7947+

2345.486 30 42 622.03 70 8667–28 2447+

2347.094 30 42 592.83 68 3878–25 7947+

2348.287 80 42 571.20 68 4814–25 9104+

2348.785 100 42 562.18 65 0137–22 4517+

2349.314 300 42 552.59 64 4148–21 8618+

2349.467 4 42 549.82 74 0365–31 4865+

Spector et al. Vol. 14, No. 3 /March 1997/J. Opt. Soc. Am. B 513

Table 1. Continued

Wavelengtha Wave number Wavelengtha Wave number(Å) Intensity (cm21) Classification (Å) Intensity (cm21) Classification

2350.367 40 42 533.53 72 6656–30 1326+

2352.118 80 42 501.87 68 4115–25 9104+

2354.107 80 42 465.96 73 7146–31 2487+

2355.992 250 42 431.99 65 1545–22 7224+

2356.437 10 42 423.97 70 8667–28 4426+

2356.690 4 42 419.42 67 8537–25 4338+

2356.953 10 42 414.69 72 0827–29 6687+

2357.690 800 42 401.43 72 0827–29 6818+

2363.142 20 42 303.61 70 7465–28 4426+

2364.811 5 42 273.75 74 0365–31 7625+

2366.002 3 42 252.48 74 0365–31 7846+

2366.953 250 42 235.51 59 6818–17 4467+

2370.536 100 42 171.68 63 3347–21 1636+

2371.256 60 42 158.87 70 2496–28 0907+

2371.985 1 42 145.91 73 1114–30 9654+

2377.094 100 42 055.34 68 5336–26 4776+

2377.183 10 42 053.76 72 1865–30 1326+

2378.234 30 42 035.18 72 9646–30 9295+

2378.858 1000 42 024.15 59 4707–17 4467+

2379.978 10 42 004.38 70 2496–28 2447+

2381.084 20 41 984.87 67 7796–25 7947+

2382.323 80 41 963.04 64 4148–22 4517+

2382.663 20 41 957.05 70 8667–28 9096+

2383.968 10 41 934.09 68 4115–26 4776+

2387.527 10 41 871.58 74 0365–32 1646+

2388.126 8 41 861.08 70 8667–29 0057+

2389.519 40 41 836.67 70 7465–28 9096+

2390.447 100 41 820.44 65 5316–23 7105+

2390.917 40 41 812.22 70 7465–28 9345+

2391.263 3 41 806.17 70 2496–28 4426+

2395.863 3 41 725.90 72 6656–30 9396+

2396.418 20 41 716.24 72 9646–31 2487+

2398.328 10 41 683.03 67 5935–25 9104+

2399.236 2 41 667.25 67 7796–26 1125+

2399.903 100 41 655.67 62 8196–21 1636+

2400.558 150 41 644.30 62 8196–21 1745+

2403.409 100 41 594.91 72 5244–30 9295+

2405.509 6 41 558.60 72 5244–30 9654+

2409.378 10 41 491.87 66 2026–24 7106+

2410.016 150 41 480.88 67 5935–26 1125+

2410.479 150 41 472.92 63 3347–21 8618+

2412.174 80 41 443.78 65 1545–23 7105+

2413.697 150 41 417.63 72 6656–31 2487+

68 5336–27 1156+

2416.099 25 41 376.46 65 5316–24 1547+

2419.344 1 41 320.96 73 0835–31 7625+

2419.961 100 41 310.43 74 0365–32 7266+

2420.593 6 41 299.65 73 0835–31 7846+

2423.770 100 41 245.52 72 0827–30 8378+

2425.596 20 41 214.47 68 5336–27 3185+

2426.533 80 41 198.56 70 8667–29 6687+

2427.305 150 41 185.46 70 8667–29 6818+

2427.623 80 41 180.06 72 9646–31 7846+

2429.591 20 41 146.70 67 8537–26 7067+

2429.636 1000 41 145.94 64 8079–23 66110+

2430.630 2 41 129.12 73 1114–31 9824+

(Table continued)

2431.422 4 41 115.39 67 5935–26 4776+

2432.551 10 41 096.64 67 0064–25 9104+

2432.747 10 41 093.33 68 4115–27 3185+

2436.985 800 41 021.87 67 8537–26 8318+

2438.185 600 41 001.68 71 9304–30 9295+

2438.995 10 40 988.07 73 7146–32 7266+

2439.248 8 40 983.82 74 0365–33 0525+

2439.519 2 40 979.27 70 2496–29 2696+

2441.577 800 40 944.73 69 8545–28 9096+

2443.038 1 40 920.24 69 8545–28 9345+

2443.116 20 40 918.94 73 0835–32 1646+

2443.332 3 40 915.32 73 1114–32 1965+

2444.377 8 40 897.83 74 3894–33 4925+

2444.573 100 40 894.55 67 0064–26 1125+

2445.227 600 40 883.61 63 3347–22 4517+

2446.722 60 40 858.63 65 0137–24 1547+

2448.169 30 40 834.48 72 0827–31 2487+

2448.997 400 40 820.68 65 5316–24 7106+

2451.278 80 40 782.70 74 0365–33 2535+

2452.561 1 40 761.36 72 5244–31 7625+

2453.705 60 40 742.36 73 7146–32 9717+

2453.965 15 40 738.04 67 8537–27 1156+

2456.306 2 40 699.22 72 1865–31 4865+

2458.595 2 40 661.33 73 7146–33 0525+

2458.652 800 40 660.39 68 3878–27 7279+

2461.461 25 40 613.99 70 7465–30 1326+

2463.472 3000 40 580.84 65 0137–24 4328+

70 2496–29 6687+

2465.675 2 40 544.58 74 0365–33 4925+

2468.334 500 40 500.91 72 6656–32 1646+

2470.196 3 40 470.38 73 7244–33 2535+

2470.767 6 40 461.03 67 7796–27 3185+

2470.819 60 40 460.18 73 7146–33 2535+

2471.261 1 40 452.95 69 8545–29 4015+

2471.804 60 40 444.06 71 9304–31 4865+

65 1545–24 7106+

2471.875 60 40 442.90 68 5336–28 0907+

2472.472 40 40 433.13 70 2496–29 8156+

2473.075 3 40 423.27 72 1865–31 7625+

2474.006 800 40 408.06 66 2026–25 7947+

2474.382 100 40 401.92 72 1865–31 7846+

2476.082 5000 40 374.19 64 8079–24 4328+

2476.483 600 40 367.65 62 8196–22 4517+

2477.092 10 40 357.73 73 0835–32 7266+

2478.915 1 40 328.05 72 5244–32 1965+

2480.474 3 40 302.70 65 0137–24 7106+

2480.808 500 40 297.28 68 3878–28 0907+

2481.354 100 40 288.41 68 5336–28 2447+

2481.382 100 40 287.96 59 4707–19 1826+

2483.128 8 40 259.63 644148–24 1547+

2484.814 60 40 232.32 73 7244–33 4925+

2485.355 500 40 223.56 64 4148–24 1909+

2486.653 60 40 202.56 74 3894–34 1875+

2488.793 20 40 168.00 71 9304–31 7625+

2490.356 800 40 142.79 68 3878–28 2447+

2493.612 30 40 090.38 68 5336–28 4426+

514 J. Opt. Soc. Am. B/Vol. 14, No. 3 /March 1997 Spector et al.

Table 1. Continued

Wavelengtha Wave number Wavelengtha Wave number(Å) Intensity (cm21) Classification (Å) Intensity (cm21) Classification

66 2026–26 1125+

2494.835 300 40 070.73 72 5244–32 4534+

2495.583 80 40 058.72 73 1114–33 0525+

2496.705 200 40 040.72 73 7244–33 6834+

2496.856 40 40 038.30 69 8545–29 8156+

2497.316 25 40 030.92 73 0835–33 0525+

2497.400 100 40 029.58 70 8667–30 8378+

2498.591 400 40 010.49 59 6818–19 6719+

2499.720 250 39 992.43 72 9646–32 9717+

2499.879 80 39 989.88 72 1865–32 1965+

2500.396 500 39 981.61 64 4148–24 4328+

2502.472 20 39 948.45 71 9304–31 9824+

2503.031 10 39 939.53 72 6656–32 7266+

2503.489 150 39 932.22 74 3894–34 4574+

2503.827 1000 39 926.83 70 8667–30 9396+

2504.407 1000 39 917.58 72 0827–32 1646+

2504.794 100 39 911.41 72 9646–33 0525+

2507.882 20 39 862.27 66 9775–27 1156+

2508.184 80 39 857.48 73 1114–33 2535+

2508.696 100 39 849.34 74 0365–34 1875+

2509.923 100 39 829.86 73 0835–33 2535+

2510.725 150 39 817.14 70 7465–30 9295+

2511.396 80 39 806.50 70 7465–30 9396+

2513.021 1 39 780.77 70 7465–30 9654+

2514.144 30 39 763.00 67 8537–28 0907+

2514.829 3 39 752.17 74 0365–34 2846+

2515.806 80 39 736.73 65 5316–25 7947+

2516.067 20 39 732.61 72 1865–32 4534+

2516.543 60 39 725.09 66 2026–26 4776+

2517.481 500 39 710.29 72 9646–33 2535+

74 3894–34 6794+

2518.514 20 39 694.01 72 6656–32 9717+

2518.810 40 39 689.34 67 7796–28 0907+

2520.727 50 39 659.16 66 9775–27 3185+

2522.996 400 39 623.50 68 5336–28 9096+

2523.250 6 39 619.51 73 1114–33 4925+

2523.664 100 39 613.01 72 6656–33 0525+

2523.942 100 39 608.65 67 8537–28 2447+

2524.560 10 39 598.95 68 5336–28 9345+

2525.341 8 39 586.71 74 3894–34 8034+

2525.796 40 39 579.58 65 0137–25 4338+

2525.827 40 39 579.09 74 0365–34 4574+

2527.865 6 39 547.18 68 4814–28 9345+

2528.509 50 39 537.11 73 7244–34 1875+

2528.664 100 39 534.69 67 7796–28 2447+

2529.112 10 39 527.68 68 5336–29 0057+

2529.160 150 39 526.94 73 7146–34 1875+

2530.747 80 39 502.15 68 4115–28 9096+

2531.130 40 39 496.17 66 2026–26 7067+

2532.661 30 39 472.30 72 9646–33 4925+

2532.723 25 39 471.34 72 5244–33 0525+

2532.918 10 39 468.30 70 4333–30 9654+

2535.399 10 39 429.68 73 7146–34 2846+

2536.550 40 39 411.79 72 6656–33 2535+

2536.637 10 39 410.44 67 8537–28 4426+

2538.465 20 39 382.06 68 3878–29 0057+

(Table continued)

2540.070 1 39 357.17 74 0365–34 6794+

2540.115 1 39 356.47 72 0827–32 7266+

2541.006 15 39 342.68 70 2714–30 9295+

2541.378 80 39 336.92 67 7796–28 4426+

2542.475 500 39 319.95 70 2496–30 9295+

2543.163 500 39 309.31 70 2496–30 9396+

2543.355 10 39 306.34 70 2714–30 9654+

2545.696 8 39 270.20 72 5244–33 2535+

2545.928 8 39 266.62 73 7244–34 4574+

2546.135 1 39 263.43 68 5336–29 2696+

2547.342 40 39 244.82 65 1545–25 9104+

2549.023 1500 39 218.95 65 0137–25 7947+

2551.549 25 39 180.12 63 3347–24 1547+

2553.494 30 39 150.28 67 5935–28 4426+

2554.022 30 39 142.19 68 4115–29 2696+

2554.604 150 39 133.27 72 1865–33 0525+

2554.699 30 39 131.81 68 5336–29 4015+

2556.247 80 39 108.12 62 8196–23 7105+

2557.928 1 39 082.42 70 8667–31 7846+

2558.092 5 39 079.91 68 4814–29 4015+

2559.811 10 39 053.68 65 5316–26 47762560.533 2 39 042.66 65 1545–26 1125

+

2562.640 400 39 010.56 68 4115–29 4015+

2563.286 20 39 000.73 70 2496–31 2487+

2564.419 25 38 983.50 70 7465–31 7625+

2564.614 100 38 980.54 64 4148–25 4338+

2567.038 1000 38 943.73 67 8537–28 9096+

2567.804 80 38 932.12 72 1865–33 2535+

2568.262 1 38 925.17 69 8545–30 9295+

2568.320 150 38 924.29 73 1114–34 1875+

2568.523 150 38 921.22 73 7244–34 8034+

2568.964 250 38 914.54 69 8545–30 9396+

2569.782 1 38 902.15 63 3347–24 4328+

2570.143 100 38 896.69 73 0835–34 1875+

2571.382 100 38 877.95 71 9304–33 0525+

2571.907 100 38 870.01 67 7796–28 9096+

2572.234 3 38 865.07 68 5336–29 6687+

2573.369 60 38 847.93 67 8537–29 0057+

2573.845 8 38 840.74 72 5244–33 6834+

2574.893 60 38 824.94 65 5316–26 7067+

2576.580 50 38 799.52 73 0835–34 2846+

2577.543 40 38 785.02 70 2714–31 4865+

2578.073 3 38 777.05 72 9646–34 1875+

2578.264 400 38 774.18 67 7796–29 0057+

2578.937 3 38 764.06 70 7465–31 9824+

2579.057 80 38 762.26 70 2496–31 4865+

2582.062 6 38 717.15 68 5336–29 8156+

2583.604 4 38 694.04 72 1865–33 4925+

2584.304 10 38 683.56 67 5935–28 9096+

2584.561 3 38 679.72 72 9646–34 2846+

2584.759 25 38 676.75 71 9304–33 2535+

2585.603 25 38 664.13 62 8196–24 1547+

2586.290 5 38 653.86 73 1114–34 4574+

2588.136 3 38 626.29 73 0835–34 4574+

2588.572 4000 38 619.78 64 4148–25 7947+

2590.173 30 38 595.91 68 4115–29 8156+

Spector et al. Vol. 14, No. 3 /March 1997/J. Opt. Soc. Am. B 515

Table 1. Continued

Wavelengtha Wave number Wavelengtha Wave number(Å) Intensity (cm21) Classification (Å) Intensity (cm21) Classification

2591.359 100 38 578.25 74 0365–35 4585+

2592.926 3 38 554.94 74 0365–35 4814+

2594.219 40 38 535.73 65 0137–26 4776+

2594.271 30 38 534.95 66 9775–28 4426+

2595.966 2 38 509.79 67 7796–29 2696+

2596.027 15 38 508.89 70 2714–31 7625+

2596.455 3 38 502.54 72 1865–33 6834+

2598.080 80 38 478.46 72 6656–34 1875+

2599.001 8 38 464.83 70 2496–31 7846+

2602.300 6 38 416.06 65 5316–27 1156+

2603.094 5 38 404.35 73 0835–34 6794+

2603.341 3 38 400.70 68 5336–30 1326+

2604.652 10 38 381.38 72 6656–34 2846+

2604.869 20 38 378.18 67 7796–29 4015+

2605.599 1 38 367.43 69 8545–31 4865+

2608.590 400 38 323.44 67 5935–29 2696+

2609.705 800 38 307.07 59 4707–21 1636+

65 0137–26 7067+

2610.799 8 38 291.02 74 3894–36 0983+

2611.585 100 38 279.49 68 4115–30 1326+

2612.047 15 38 272.72 74 3894–36 1174+

2613.789 6 38 247.22 71 9304–33 6834+

2618.033 10 38 185.22 67 8537–29 6687+

2623.032 4 38 112.45 66 2026–28 0907+

2623.101 6 38 111.45 67 7796–29 6687+

2624.482 40 38 091.40 69 8545–31 7625+

2625.575 3 38 075.54 70 2714–32 1965+

2626.088 10 38 068.10 66 9775–28 9096+

2627.151 1 38 052.70 70 2496–32 1965+

2627.776 20 38 043.65 66 9775–28 9345+

2628.213 40 38 037.32 67 8537–29 8156+

2629.400 2 38 020.16 70 7465–32 7266+

2633.316 20 37 963.62 67 7796–29 8156+

2633.704 1000 37 958.02 66 2026–28 2447+

2636.376 2 37 919.56 74 0365–36 1174+

2637.672 500 37 900.92 63 3347–25 4338+

2637.861 300 37 898.21 65 0137–27 1156+

2639.689 80 37 871.96 69 8545–31 9824+

2641.593 3 37 844.67 72 5244–34 6794+

2643.325 300 37 819.88 59 6818–21 8618+

2643.433 6 37 818.33 70 2714–32 4534+

2646.309 4 37 777.23 67 5935–29 8156+

2650.256 30 37 720.97 72 5244–34 8034+

67 8537–30 1326+

2651.169 800 37 707.98 64 4148–26 7067+

66 9775–29 2696+

2652.480 3 37 689.35 69 8545–32 1646+

2654.690 3 37 657.97 69 8545–32 1965+

2655.041 80 37 652.99 73 1114–35 4585+

2655.447 2 37 647.24 67 7796–30 1326+

2656.676 80 37 629.82 73 1114–35 4814+

2656.983 150 37 625.48 73 0835–35 4585+

73 7244–36 0983+

2658.179 300 37 608.55 59 4707–21 8618+

2658.506 1 37 603.92 68 5336–30 9295+

2658.626 10 37 602.23 73 0835–35 4814+

(Table continued)

2659.256 80 37 593.32 68 5336–30 9396+

2659.983 20 37 583.04 64 4148–26 8318+

2660.452 10 37 576.42 66 9775–29 4015+

2662.297 6 37 550.38 68 3878–30 8378+

2663.012 80 37 540.30 63 3347–25 7947+

2664.247 5 37 522.90 70 2496–32 7266+

2664.755 30 37 515.75 68 4814–30 9654+

2666.423 30 37 492.27 70 7465–33 2535+

2667.104 100 37 482.71 68 4115–30 9295+

2667.863 20 37 472.04 68 4115–30 9396+

2668.662 80 37 460.82 67 5935–30 1326+

2669.691 1 37 446.39 68 4115–30 9654+

2670.062 3000 37 441.18 65 5316–28 0907+

2716.479 5 36 801.45 66 2026–29 4015+

69 8545–33 0525+

2758.153 100 36 245.43 65 1545–28 9096+

2766.954 4 36 130.15 65 5316–29 4015+

2770.988 150 36 077.56 67 0064–30 9295+

2778.806 15 35 976.06 70 4333–34 4574+

2780.178 1 35 958.31 68 4115–32 4534+

2791.396 4 35 813.81 71 9304–36 1174+

2821.763 20 35 428.41 68 4814–33 0525+

2824.279 20 35 396.85 67 5935–32 1965+

2827.300 30 35 359.03 68 4115–33 0525+

2834.148 80 35 273.60 66 2026–30 9295+

2835.003 80 35 262.96 66 2026–30 9396+

2836.131 4000 35 248.93 59 6818–24 4328+

2836.465 200 35 244.79 63 3347–28 0907+

2837.878 250 35 227.24 68 4814–33 2535+

2843.472 25 35 157.94 68 4115–33 2535+

2844.940 300 35 139.80 67 5935–32 4534+

2848.950 2000 35 090.34 63 3347–28 2447+

2853.236 5000 35 037.63 59 4707–24 4328+

2866.038 2 34 881.13 65 0137–30 1326+

2871.669 3000 34 812.74 66 9775–32 1646+

2873.485 10 34 790.73 70 2496–35 4585+

2878.230 2 34 733.39 64 4148–29 6818+

2878.602 100 34 728.90 62 8196–28 0907+

2878.779 15 34 726.76 67 7796–33 0525+

2879.673 5 34 715.98 66 2026–31 4865+

2886.875 200 34 629.38 70 7465–36 1174+

2889.132 600 34 602.32 65 5316–30 9295+

2891.457 1000 34 574.50 62 8196–28 2447+

2893.231 60 34 553.31 67 0064–32 4534+

2894.312 200 34 540.40 67 5935–33 0525+

2895.552 250 34 525.61 67 7796–33 2535+

2903.976 2000 34 425.46 63 3347–28 9096+

2908.437 4 34 372.66 69 8545–35 4814+

2910.700 10 34 345.94 68 5336–34 1875+

2911.270 80 34 339.21 67 5935–33 2535+

2911.618 30 34 335.11 70 4333–36 0983+

2912.089 2 34 329.56 63 3347–29 0057+

2913.170 300 34 316.82 70 4333–36 1174+

2915.105 400 34 294.04 68 4814–34 1875+

2920.915 1500 34 225.83 65 1545–30 9295+

2921.011 80 34 224.71 68 4115–34 1875+

516 J. Opt. Soc. Am. B/Vol. 14, No. 3 /March 1997 Spector et al.

Table 1. Continued

Wavelengtha Wave number Wavelengtha Wave number(Å) Intensity (cm21) Classification (Å) Intensity (cm21) Classification

2921.829 800 34 215.13 65 1545–30 9396+

2925.419 400 34 173.14 70 2714–36 09832926.986 40 34 154.84 70 2714–36 1174

+

2936.457 3 34 044.69 65 5316–31 4865+

2937.048 2 34 037.84 66 2026–32 1646+

2937.163 2 34 036.50 59 4707–25 4338+

2938.268 40 34 023.71 68 4814–34 4574+

2939.752 60 34 006.53 66 2026–32 1965+

2944.276 60 33 954.29 68 4115–34 4574+

2944.306 80 33 953.94 67 0064–33 0525+

2948.161 1500 33 909.54 62 8196–28 9096+

67 5935–33 6834+

2950.110 4000 33 887.13 59 6818–25 7947+

2956.518 15 33 813.69 62 8196–29 0057+

2961.860 8 33 752.71 67 0064–33 2535+

2964.404 4 33 723.74 66 9775–33 2535+

2968.629 5000 33 675.75 59 4707–25 7947+

2969.307 10 33 668.06 65 1545–31 4865+

2969.407 1 33 666.93 63 3347–29 6687+

2975.999 80 33 592.36 67 7796–34 1875+

2982.904 1 33 514.60 67 0064–33 4925+

3015.625 1 33 150.97 62 8196–29 6687+

3031.696 300 32 975.24 59 6818–26 7067+

3032.003 40 32 971.90 08–32 9717+

3033.696 3 32 953.50 68 4115–35 4585+

3034.139 30 32 948.69 66 2026–33 2535+

3035.839 6 32 930.24 68 4115–35 4814+

3037.381 8 32 913.52 67 5935–34 6794+

3043.229 20 32 850.27 59 6818–26 8318+

3043.387 20 32 848.57 65 0137–32 1646+

3048.781 60 32 790.46 66 9775–34 1875+

3048.821 50 32 790.03 67 5935–34 8034+

3057.841 1 32 693.31 66 9775–34 2846+

3058.459 100 32 686.70 62 8196–30 1326+

3070.397 8 32 559.62 65 5316–32 9717+

3076.229 30 32 497.89 63 3347–30 8378+

3078.062 300 32 478.54 65 5316–33 0525+

3082.795 1 32 428.68 65 1545–32 7266+

3085.984 800 32 395.17 63 3347–30 9396+

3088.940 3 32 364.17 68 4814–36 1174+

3095.570 20 32 294.85 68 4115–36 1174+

3104.350 1 32 203.52 67 0064–34 8034+

3122.586 10 32 015.46 66 2026–34 1875+

3128.534 80 31 954.59 59 6818–27 7279+

3133.807 3 31 900.83 65 1545–33 2535+

3135.923 2 31 879.30 62 8196–30 9396+

3171.735 20 31 519.37 66 9775–35 4585+

3180.046 150 31 437.00 59 6818–28 2447+

aMeasured in air.

3190.678 2 31 332.24 62 8196–31 4865+

3207.294 8 31 169.93 63 3347–32 1646+

3221.998 150 31 027.68 59 4707–28 4426+

3241.913 150 30 837.08 08–30 8378+

3253.305 10 30 729.11 65 0137–34 2846+

3258.901 20 30 676.35 59 6818–29 0057+

3281.515 20 30 464.95 59 4707–29 0057+

3318.735 400 30 123.29 41617–34 2846+

3369.659 4000 29 668.07 08–29 6687+

3381.401 10 29 565.05 62 8196–33 2535+

3469.938 200 28810.71 41617–32 9717+

3499.785 80 28565.01 41617–32 7266+

3539.480 2000 28244.67 08–28 2447+

3558.948 3000 28090.17 08–28 0907+

3605.547 40 27727.13 08–27 7279+

3619.139 4000 27623.01 41617–31 7846+

3725.918 100 26831.39 08–26 8318+

3743.353 4000 26706.43 08–26 7067+

3747.643 20 26675.86 41617–30 8378+

3788.385 600 26388.98 71036–33 4925+

3864.559 2 25868.84 71036–32 9717+

3875.665 100 25794.71 08–25 7947+

3896.803 4000 25654.79 41617–29 8156+

3919.405 2000 25506.85 41617–29 6687+

3930.640 4000 25433.95 08–25 4338+

3936.763 30 25394.39 92855–34 6794+

3984.023 100 25093.16 71036–32 1965+

4050.531 400 24681.15 71036–31 7846+

4054.033 100 24659.83 71036–31 7625+

4097.473 400 24398.40 92855–33 6834+

4099.936 150 24383.74 71036–31 4865+

4117.196 2 24281.53 41617–28 4426+

4224.309 30 23665.84 11 0134–34 6794+

4355.298 10 22954.09 41617–27 1156+

4363.467 30 22911.12 92855–32 1965+

4401.556 800 22712.86 71036–29 8156+

4404.605 20 22697.14 92855–31 9824+

4409.844 10 22670.17 41617–26 8318+

4409.899 800 22669.89 11 0134–33 6834+

4430.406 20 22564.96 71036–29 6687+

4434.277 100 22545.26 41617–26 7067+

4443.383 2 22499.04 92855–31 7846+

4447.602 60 22477.72 92855–31 7625+

4483.404 10 22298.23 71036–29 4015+

4502.913 10 22201.62 92855–31 4865+

4510.031 200 22166.58 71036–29 2696+

4572.888 100 21861.89 08–21 8618+

5019.823 60 19915.49 11 0134–30 9295+

3. ANALYSISIt is well known that the 4f n6s and the 4f n6p levels ofthe third spectra of the rare earths do not interactstrongly with other configurations and that the radial en-ergy integrals for these configurations are nearly constantacross this period.4 Also, the spin-orbit parameters, al-

though not nearly constant, are known for many lan-thanide third spectra and can be interpolated accurately.Therefore we were able to carry out an accurate calcula-tion of the energy-level values for these configurations inDy III by interpolating values for the parameters. Fur-thermore, the strongest lines of these spectra are knownto arise from transitions between these configurations.

Spector et al. Vol. 14, No. 3 /March 1997/J. Opt. Soc. Am. B 517

We thus began by searching the line list for the lowest in-tervals of the 4f 96p configuration. These were expectedto be long chains of line pairs because this configurationcombines with both the 4f96s and the 4f 95d configura-tions, the latter being in intermediate coupling and thusproviding many combinations.Indeed, this search proved successful and opened the

way for the discovery of many more levels. As notedabove, the 4f 95d levels found in this way did not combinestrongly with the 4f10 5I ground term because they wereseptet terms and would require a spin change of 1. Atthe same time, J.-F. Wyart,5 working independently witha small list of lines measured by Hussain6 and identifiedas Dy III by Aikman et al.,7 found the intervals of theground 5I term by combination with a few upper 4f 95dquintet levels. Some of these levels, through intermedi-ate coupling present in this upper configuration, had suf-ficient septet character to enable us to connect the twosystems.

A. 4f 96s–4f 96p TransitionsMore than 150 lines are classified in this array. The cou-pling scheme is J1 j in both configurations. The high pu-rity of the eigenvectors in this scheme can be seen inTable 2 below as well as in Figs. 1 and 2, where the levelsbuilt on the same core states are connected. In the caseof the 4f 96s configuration (Fig. 1) the pairs of levels dueto the coupling of the 6s1/2 spin to each core level are evi-dent. In Fig. 2 the 4f 96p levels are shown. For j(6p)5 1/2 (denoted by p2) the pairs of levels are again evi-dent, and for j 5 3/2 (denoted as p1) four levels are ob-tained per core level.The lines allowed by the core selection rule DJ1 5 0

represent approximately 90% of the estimated intensity

in the classified array. We consider this as strong sup-port for the classifications. The 6s1/2–6p1/2 and the6s1/2–6p3/2 transitions are in the concentrated spectralranges 2969–2836 Å and 2588–2438 Å, respectively. Theseparation of the two groups is due to the 6p spin-orbitsplitting. The other 6s–6p transitions are scattered inthe wider range of 3381–2198 Å.

B. 4f 95d–4f 96p TransitionsIntermediate coupling conditions prevail for most of the4f 95d levels. This results in a large number of classifiedlines (60% of the total classified and 50% of the intensi-ties). The strongest of these transitions have wave-lengths shorter than 2500 Å. The level structure of the4f 95d configuration is shown in Fig. 3. Only the lowestfew terms exhibit LS coupling.

C. 4f 10–4f 95d TransitionsThere are 39 lines classified as 4f–5d transitions. How-ever, Dy III should have transitions in the visible and theinfrared regions, as have the closest elements Tb and Ho.Our attempts to determine higher terms of the 4f10 con-figuration failed. Extension of the observations of thisarray beyond 5000 Å is undoubtedly needed in order tocontinue the analysis.The energy levels derived in this analysis of Dy III are

given in Table 2. Their uncertainty, as defined by thelevel optimization code in Ref. 3 is 60.03 cm21. Approxi-mately 85% of the level values are uncertain to withinthis figure. Although the leading eigenvector percent-ages of the 4f 95d levels are low on the average, we groupthem into LS terms if their highest component is greaterthan 39%. If the first component is less than 40% but thefinal terms of the first and the second components are the

Fig. 1. Energy levels of the 4f 96s configuration connected in Ji j-coupling terms. The bars joined by dotted lines represent unknownlevels built on 6H and 6F parent states.

518 J. Opt. Soc. Am. B/Vol. 14, No. 3 /March 1997 Spector et al.

Fig. 2. Energy levels of the 4f 96p configuration connected inJi j-coupling terms. The dotted bars represent unknown levels.The symbols p2 and p1 refer to p1/2 and p3/2 j states of the 6pelectron.

Fig. 3. Energy levels of the 4f 95d configuration connected inLS-coupling terms. The dotted pairs of levels are the knownlow-lying 4f 96s levels.

same and sum to greater than 40%, the level is includedin the term corresponding to the largest component.

4. THEORYAll the levels of the excited configurations have been in-terpreted in the framework of the Slater–Racah paramet-ric method8 by means of the chain of programs in use atOrsay, France. Complete sets of basis states were usedin separate studies of each configuration. The initial setof parameter values used in the first diagonalization wasobtained by interpolation of fitted parameters availablefor most of the third spectra of the rare earths. An initialmatchup of the observed levels to those calculated wasused to adjust the parameter values and to recalculatethe levels. When this iterative process was completed af-ter all the currently known levels were included, the av-erage deviations from the calculated levels were 616,629, and 649 cm21 for the 4f 96p, the 6s, and the 5d con-figurations, respectively.The final fitted values of the parameters are given in

Table 3 along with their standard errors. The final cal-culated eigenvectors were used to calculate magneticg-factors, which are given in Table 2.

Configuration Mixing EffectsThe present theoretical studies confirm the importance ofeffective parameters of far configuration interaction forachieving a good fit of the calculations to the observed en-ergy levels, especially the forbidden Slater parameters9

Dk and Yk . The parameters a, b, and g, which representthe 4f 9 core corrections aL1(L1 1 1) 1 12bG(G2)1 10gG(R7), have been fixed in the parameter fit be-cause only one core term is known. The following threepoints show that the mixing between close configurationsin the present study has little effect:

1. The deviations Eexp 2 Eth for the three separateconfigurations are small.2. Only two observed lines make the forbidden transi-

tion 4f–6s. In particular, the levels 28 244 with J 5 7(the third lowest level of 4f 96s) and 28 090 with J 5 7(4f 95d) have similar combinations with 4f 96p levels, andboth decay to 4f10 5I8 with strong and nearly equally in-tense lines.3. Although 4f 85d2 might well overlap 4f 96p accord-

ing to Brewer,10 the deviations DE are as small as inother 4f N6p isoionic configurations (N 5 10 to 13), andthe energy parameters fit perfectly the trends of theneighboring elements3 Ho III–Yb III.

5. IONIZATION ENERGYValues for the ionization energies of the doubly and thetriply ionized rare earths were calculated by Sugar andReader,11 based on the assumption of a constant value forthe 4f N216s 2 4f N217s effective quantum number differ-ence Dn* 5 n* (6s) 2 n* (7s), assumed to be 1.048, andinterpolated values for the energies of the configurations.These interpolated energies comprise the system differ-ence SD of 4f N 2 4f N215d (between lowest levels),the energy difference DE 5 4f N216s2 4f N215d (be-

Spector et al. Vol. 14, No. 3 /March 1997/J. Opt. Soc. Am. B 519

Table 2. Dy III Energy Levels and Their Percentage Composition

ComponentsLevel (%) Low (%)

Configuration Term J (cm21) 1st 2nd Componentsa g Calc.

4f10 5I 8 0.007 4161.226 7103.085 9285.174 11 013.69

4f 9(6H)5d 7H 8 16 453.19 76 11 (6H)5d 7I 1.3557 17 446.29 62 15 (6H)5d 7G 1.3236 19 182.51 51 17 (6H)5d 7G 1.3165 21 174.68 64 12 (6H)5d 7G 1.2114 22 722.93 69 10 (6F)5d 7H 1.061

4f 9(6H)5d 7I 9 19 671.28 86 6 (6H)5d 7K 1.3198 21 861.89 60 13 (6H)5d 5I 1.2837 24 154.89 41 23 (6H)5d 7G 1.2926 24 710.82 61 8 (6H)5d 7G 1.1845 26 112.23 70 4 (6H)5d 5H 1.047

4f 9(6H)5d 7F 6 21 163.38 57 16 (6H)5d 7H 1.4295 23 710.98 48 20 (6F)5d 7F 1.4404 25 910.06 33 21 (6F)5d 7F 1.472

4f 9(6H)5d 7G 7 22 451.40 54 30 (6H)5d 7I 1.3386 26 477.79 44 13 (6H)5d 5G 1.352

4f 9(6H)5d 7K 10 23 661.08 94 5 (4I3)5d 5L 1.2949 27 727.14 57 38 (6H)5d 5K 1.2388 26 831.40 46 31 (6H)5d 5K 1.1937 28 090.20 59 11 (6H)5d 5K 1.1316 29 269.69 56 21 (6H)5d 5I 1.029

4f 9(6H)5d 5K 9 24 190.95 52 33 (6H)5d 7K 1.2368 30 837.08 58 30 (6H)5d 7K 1.1767 32 971.89 53 17 (6H)5d 7K 1.124

4f 9(6H15/2)6s1/2 8 24 432.81 94 5 (4I15/21)6s1/2 1.3687 25 794.68 88 6 (6H13/2)6s1/2 1.294

4f 9(6H)5d 5I 8 25 433.95 70 12 (6H)5d 7K 1.2417 29 668.06 41 16 (6H)5d 7I 1.191

4f 9(6H)5d 5H 7 26 706.50 49 28 (6H)5d 5I 1.2454f 9(6H)5d 5G 6 27 115.33 55 19 (6H)5d 7G 1.327

5 29 401.30 43 11 (6H)5d 5F 1.2884 31 982.30 52 8 (6H)5d 5H 1.318

4f 95d 5 27 318.56 38 26 (6F)5d 7D (6H)5d 7G 1.4554f 9(6H13/2)6s1/2 7 28 244.68 91 6 (6H15/2)6s1/2 1.318

6 28 909.55 82 15 (6H11/2)6s1/2 1.2534f 95d 6 28 442.76 35 28 (6F)5d 7F (6F)5d 7G 1.4084f 95d 5 28 934.06 33 30 (6H)5d 7G (6F)5d 7D 1.4414f 9(6F)5d 7H 7 29 005.42 41 27 (6F)5d 7G 1.341

8 29 681.14 84 6 (6H)5d 7H 1.3604f 95d 6 29 815.94 39 16 (6H)5d 5H (6H)5d 5I 1.2024f 95d 6 30 132.35 34 16 (6F)5d 7H (6F)5d 7F 1.2834f 9(6H11/2)6s1/2 5 30 929.13 77 17 (6H9/2)6s1/2 1.179

6 30 939.78 76 15 (6H13/2)6s1/2 1.2504f 95d 4 30 965.50 38 15 (6F)5d 7G (6F)5d 7H 1.2174f 9(6F)5d 7G 7 31 248.18 66 16 (6F)5d 7H 1.388

6 32 726.18 42 13 (6F)5d 7F 1.3574f 95d 5 31 486.80 23 18 (6H)5d 5F (6F)5d 7H 1.3074f 95d 5 31 762.85 22 21 (6H)5d 5H (6H)5d 5F 1.2404f 95d 6 31 784.22 39 12 (6H)5d 5I (6H)5d 7I 1.1194f 9(6F11/2)6s1/2 6 32 164.97 92 4 (6H11/2)6s1/2 1.482

(Table continued)

520 J. Opt. Soc. Am. B/Vol. 14, No. 3 /March 1997 Spector et al.

Table 2. Continued

ComponentsLevel (%) Low (%)

Configuration Term J (cm21) 1st 2nd Componentsa g Calc.

5 34 187.22 53 39 ( 6F9/2)6s1/2 1.4054f 95d 5 32 196.20 20 18 (6H)5d 5I (6H)5d 5H 1.1544f 9(6H9/2)6s1/2 4 32 453.42 78 16 (6H7/2)6s1/2 1.037

5 33 052.82 54 16 (6F11/2)6s1/2 1.2334f 9(6F9/2)6s1/2 5 33 253.99 37 27 (6F11/2)6s1/2 1.362

4 34 457.60 68 22 (6F7/2)6s1/2 1.4334f 95d 5 33 492.04 34 10 (6H)5d 6I (6H)5d 5H 1.0564f 95d 4 33 683.59 36 15 (6H)5d 5H (6H)5d 5I 0.9804f 95d 6 34 284.47 35 31 (6F)5d 5G (6F)5d 5H 1.2764f 95d 4 34 679.54 21 21 (6H)5d 5I (6F)5d 7G 1.1344f9(6H7/2)6s1/2 4 34 803.16 77 16 (6H9/2)6s1/2 0.9264f 95d 5 35 458.37 30 26 (6F)5d 5F (6F)5d 5G 1.3194f 95d 4 35 481.64 24 24 (6H)5d 5F (6F)5d 5D 1.3804f 9(6F7/2)6s1/2 3 36 098.72 63 28 (6F5/2)6s1/2 1.426

4 36 117.00 70 21 (6F9/2)6s1/2 1.3884f 9(6H15/2)6p1/2 7 59 470.43 93 6 (4I15/21)6p1/2 1.365

8 59 681.76 88 6 (6H15/2)6p3/2 1.3124f 9(6H13/2)6p1/2 6 62 819.06 90 4 (6H15/2)6p3/2 1.315

7 63 334.96 92 4 (6H13/2)6p3/2 1.2624f 9(6H15/2)6p3/2 8 64 414.48 87 5 (6H15/2)6p1/2 1.303

9 64 807.02 94 6 (4I15/21)6p3/2 1.3267 65 013.56 92 5 (4I15/21)6p3/2 1.3286 66 202.72 59 27 (6H11/2)6p1/2 1.286

4f 9(6H11/2)6p1/2 5 65 154.88 86 4 (6H13/2)6p3/2 1.2386 65 531.42 62 20 (6H15/2)6p1/2 1.230

4f 9(6H9/2)6p1/2 4 67 006.70 85 5 (6H11/2)6p3/2 1.0955 67 593.14 89 4 (4G19/2)6p1/2 1.062

4f 9(6F11/2)6p1/2 5 66 977.71 93 4 (4G11/22)6p1/2 1.5236 67 779.54 62 18 (6H13/2)6p1/2 1.352

4f 9(6H13/2)6p3/2 7 67 853.29 87 4 (6H11/2)6p1/2 1.2678 68 387.48 95 3 (4I13/2)6p3/2 1.2816 68 533.09 73 19 (6F11/2)6p1/2 1.3255 69 854.28 67 16 (6F9/2)6p1/2 1.266

4f 9(6F9/2)6p1/2 5 68 411.88 60 19 (6H13/2)6p1/2 1.3314 68 481.23 84 9 (4F9/21)6p1/2 1.498

4f 9(6H11/2)6p3/2 6 70 249.03 80 6 (6H9/2)6p3/2 1.2065 70 746.31 76 9 (6F9/2)6p3/2 1.2727 70 866.62 84 5 (6F11/2)6p3/2 1.2264 71 930.79 65 12 (6F7/2)6p1/2 1.254

4f 9(F11/2)6p3/2 7 72 082.64 89 6 (6H11/2)6p3/2 1.4096 72 665.81 74 14 (6H9/2)6p3/2 1.3945 73 083.86 82 7 (6F9/2)6p3/2 1.4414 73 111.48 84 5 (6F9/2)6p3/2 1.490

4f 9(6F7/2)6p1/2 4 70 271.82 65 16 (6H11/2)6p3/2 1.2973 70 433.78 83 5 (6P5/2)6p1/2 1.419

4f 9(6H9/2)6p3/2 5 72 186.11 77 8 (6H7/2)6p3/2 1.1024 72 524.17 71 10 (6F7/2)6p1/2 1.2066 72 964.28 73 13 (6H9/2)6p3/2 1.151

4f 9(6F9/2)6p3/2 6 73 714.17 80 8 (4F9/21)6p3/2 1.3795 74 036.62 76 9 (4F9/21)6p3/2 1.3864 74 389.82 72 8 (4F9/21)6p3/2 1.417

4f 9(6H7/2)6p3/2 4 73 724.34 76 10 (6H9/2)6p3/2 0.906

aThis column contains either the second component of the designated level or the first two components of the undesignated level (no percentage is 40 orhigher).

Spector et al. Vol. 14, No. 3 /March 1997/J. Opt. Soc. Am. B 521

Table 3. Energy Parameters and Standard Error for the 4f 95d, 4f 96s, and 4f 96p Configurations of Dy III

Parameter(cm21) 4f 95d 4f 96s 4f 96p

A 38 186 60 35 295 27 74 036 28E1 6285 f a 6244 f 6284 44E2 34.1 f 33.9 f 34.0 0.8E3 623.8 6 610 3 628.6 2F2(fd) 20 619 180F4(fd) 14 684 270G1(fd) 8460 190G3(fd) 9410 410G5(fd) 6457 310G3(fs) 2117 40F2(fp) 5925 60G2(fp) 1878 40G4(fp) 1525 70zf 1932.9 9 1922.3 8 1934.3 3zd 1019 15zp 3346.1 7D1 8.1 1 12.9 1Y2 268 5Y4 2522 ra

a 24 f 28.9 f 24 fb 200 f 241 f 200 fg 262 f 274.7 f 262 fObserved levels 50 15 37Calculated levels 1878 396 1168Average error (cm21) 49 29 16

a f, fixed parameter; r, ratio of Y2/Y4 held constant.

tween lowest levels), the position of the center of gravityof the levels of 4f N216s based on the first parent termand calculated with G1(f, s) 5 2870 cm21, andthe interval DT 5 4f N216s 2 4f N217s, interpolated as80 800 cm21. From these quantities the term valueT(4f N216s) and the ionization energy may be derived.With the newly observed energy levels of Dy III, we knowthe quantities SD and DE to be 16453.19 cm21 and7979.62 cm21, respectively, and the ionization energy maybe derived from them with reduced uncertainty. Usingthe procedure outlined in Ref. 11, we obtain a value forthe ionization energy of 184 970 6 800 cm21, where theuncertainty is due only to the interpolated value of DT.The uncertainty given in Ref. 11 is 2400 cm21.

ACKNOWLEDGMENTSJ.-F. Wyart is grateful to A. Bachelier and J. Sinzelle,who enabled him to perform the parametric calculationsat the Paris-Sud-Informatique computer center. J.Sugar was partly supported by the U.S. National Aero-nautics and Space Administration.

REFERENCES1. J. Sugar, ‘‘Analysis of the third spectrum of praseody-

mium,’’ J. Opt. Soc. Am. 53, 831 (1963).

2. V. Kaufman and B. Edlen, ‘‘Reference wavelengths fromatomic spectra in the range 15 Å to 25000 Å,’’ J. Phys.Chem. Ref. Data 3, 825 (1974).

3. The program ELCALC was written by L. J. Radziemski, Jr.(Washington State University, Pullman, Washington,99163). The procedure and definition of level value uncer-tainties are described by L. J. Radziemski, Jr. and V. Kauf-man, J. Opt. Soc. Am. 159, 424 (1969).

4. J.-F. Wyart and C. Bauche-Arnoult, ‘‘Interpretation desconfigurations 4f N5d et 4f N6s par la methodeparametrique generalisse,’’ Phys. Scr. 22, 583 (1981).

5. J.-F. Wyart, ‘‘Workshop on laboratory and astronomicalhigh resolution spectra,’’ in APS Conf. Series 81, A. J. Sau-val, R. Blomme, and N. Grevesse, eds. (American PhysicalSociety, Washington, D.C., 1994), p. 182.

6. R. Hussain, ‘‘The spectra of Dy IV and Ho III,’’ Ph.D. disser-tation (Johns Hopkins University, Baltimore, Maryland,1973).

7. G. C. L. Aikman, C. R. Cowley, and H. M. Crosswhite, ‘‘Dys-prosium III in the spectra of peculiar A and B stars,’’ Astro-phys. J. 232, 812 (1979).

8. R. D. Cowan, The Theory of Atomic Structure and Spectra(U. California Press, Berkeley, Calif., 1981).

9. J.-F. Wyart, J. Blaise, and P. Camus, ‘‘Progres recents dansl’interpretation des configurations 4f N(5d 1 6s) des lan-tanides,’’ Phys. Scr. 9, 325 (1974).

10. L. Brewer, ‘‘Energies of the electronic configurations of thesingly, doubly, and triply ionized lanthanides,’’ J. Opt. Soc.Am. 59, 2083 (1971).

11. J. Sugar and J. Reader, ‘‘Ionization energies of doublyand triply ionized rare earths,’’ J. Chem. Phys. 59, 2083(1973).