Date post: | 28-Dec-2015 |
Category: |
Documents |
Upload: | cameron-chapman |
View: | 217 times |
Download: | 1 times |
The Millimeter/Submillimeter Spectrum of the CCP (X2r) Radical
DeWayne T. HalfenSteward Observatory, Arizona Radio Observatory, University of Arizona
Dennis ClouthierDepartment of Chemistry, University of Kentucky
Lucy M. ZiurysDepartments of Chemistry and Astronomy, Steward Observatory, Arizona
Radio Observatory, University of Arizona
June 20, 2008
Why CCP ?Why CCP ?
• Chemical aspect– Dicarbides have 2 possible structures:
cyclic T-shaped or linear
– Cyclic: NaC2, MgC2, AlC2, SiC2 (Largo et al.
2004; Chasovskikh et al. 2007; Thaddeus et al. 1984)
– Linear: CCS, CCCl (Saito et al. 1987; Sumiyoshi et al. 2003)
• Astronomical Aspect– Five phosphorus-bearing molecules found in
circumstellar envelopes, including CP and HCP (Guélin et al. 1990; Agúndez et al. 2007; Milam et al. 2008)
– Multiple carbon-chain species present as well, up to C8
– CCP is next logical molecule to search for (see FD07)
Phosphorus-bearing
species in space
PN CP HCP
PO PH3
Are there more?
TA
* (K
) 0.00
0.01
-146 -86 -26 34 94
0.00
0.01
CP: N = 5 4 IRC +10216
J = 5.5 4.5
VLSR (km s-1)
J = 4.5 3.5
13CC3H
C4H
C4H
29SiC2C4H
U
NaCN
U
Milam et al. 2008
• Theoretical calculations by Largo et al. (1994), El-Yazal et al. (1997), and Sunahori, Wie, Clouthier (2007)– Predicted linear CCP structure and
2r ground state
– Calculated the bond lengths, dipole moment (3.3-3.6 D), and vibrational frequencies
• First detected in lab by Sunahori, Wie, Clouthier (2007)– Measured LIF and wavelength-
resolved emission spectrum of the 2–X2r transition
Sunahori, Wie, Clouthier 2007
Past Work on CCPPast Work on CCP
Millimeter-wave Direct Absorption SpectrometerMillimeter-wave Direct Absorption Spectrometer
Detector
RadiationSource
Gas Cell
Reactant
Gas-Phase Synthesis of CCPGas-Phase Synthesis of CCP
• Gas-phase P source– Glass oven in an
attachment at the end of the cell
– Heated red phosphorus to 300oC
• Added 1-2 mtorr of acetone free HCCH– Dry Ice/Acetone trap
necessary (-80oC)
• 40 mtorr of Ar carrier gas also added
• AC discharge – 200 W at 600 – Blue glow in cell Gas-phase P source
Ring Electrodes Glass Attachment
Sample Oven
Cooling Jacket+ -
Caution: Red P + heat in vacuum makes white P
0.6
0.4
0.2
0.0
410409408407406405404403402401400399x10
3
0.6
0.4
0.2
0.0
383382381380379378377376375374x10
3
0.6
0.4
0.2
0.0
397396395394393392391390389388387x10
3
0.6
0.4
0.2
0.0
370369368367366365364363362361x10
3
0.6
0.4
0.2
0.0
423422421420419418417416415414413412x10
3
J' = 32.5
J' = 31.5
J' = 30.5
J' = 29.5
J' = 28.5
Rotational Spectrum of CCP (X2r)
Rotational Spectrum of CCP (X2r)
• Initially searched 30 GHz– Used predictions based on
Sunahori et al. (2007) study
– Identified doublets decreasing in separation with increasing frequency
– = 1/2 of a 2r state
• Searched for = 3/2 state– Conditions optimized
– Another 25 GHz selectively scanned
– = 3/2 identified as doublet increasing in separation with increasing frequency
– v2 = 1 also observed
= 1/2
= 3/2 v2 = 1
CCP Search Stick Spectrum
• = 1/2 and 3/2 spin-orbit ladders, e and f lambda-doublets
• Phosphorus hyperfine I(P) = 1/2 observed at low frequency
133620133600133580
413305413285413265
273525273505273485
J = 10.5 9.5
J = 21.5 20.5
J = 32.5 31.5e f
e f
e f 10 9F = 11 1010 9F = 11 10
Frequency (MHz)
CCP (X2r) = 1/2
340221340201340181
532368532348532328
417133417113417093
J = 26.5 25.5
J = 32.5 31.5
J = 41.5 40.5
e f
e f
e/f
Frequency (MHz)
CCP (X2r) = 3/2
Halfen, Sun, Clouthier, Ziurys 2008
-30
-20
-10
0
10
20
30
40
50
7.5 12.5 17.5 22.5 27.5 32.5 37.5 42.5
L-t
ype
do
ub
ling
(M
Hz)
J'
L-type doubling vs. J'
= 1/2
= 3/2
413304413284413264
464090464070464050
438700438680438660
J = 32.5 31.5
J = 34.5 33.5
J = 36.5 35.5f e
e/f
e f
Frequency (MHz)
CCP (X2r) = 1/2
• 33 = 1/2 transitions measured from 120-540 GHz
• 18 = 3/2 transitions recorded from 301-545 GHz
• 113 lines measured
• Fine structure resolved for most transitions
Selected Rotational Frequencies of CCP (X 2r)
J J F F Parity obs obs - calc
10.5 9.5 11 10 1/2 e 133577.511 0.04410 9 1/2 e 133579.049 0.00811 10 1/2 f 133623.741 -0.00610 9 1/2 f 133625.600 0.016
21.5 20.5 a 1/2 e 273489.512 0.010a 1/2 f 273519.557 -0.019
26.5 25.5 a 3/2 e 340200.936 0.094a 3/2 f 340200.936 0.094
32.5 31.5 a 1/2 e 413281.401 -0.009a 1/2 f 413287.070 -0.009a 3/2 e 417112.006 -0.037
41.5 40.5 a 3/2 f 417113.597 0.034a 3/2 e 532346.287 0.019a 3/2 f 532349.624 -0.057
Transition Frequencies of CCP (X2r)Transition Frequencies of CCP (X2r)
Spectroscopic Constants for CCPParameter This work (MHz) Theoretical
B 6392.4138(26) 6390a, 6367b
D 0.0022595(22)H 9.50(59) x 10-9
A 4212195c
AD 40.536(10)AH -2.782(86) x 10-4
AL 4.8(2.3) x 10-9
p+2q 50.0127(96)(p+2q)D -0.015124(47)(p+2q)H 7.29(21) x 10-7
q 0.0109c
qD 6.57(17) x 10-5
h1/2 484.220(30)h1/2D 0.8337(91)d1/2 632.538(16)rms 0.050
a Sunahori et al. (2008) b El-Yazal et al. (1997) c Held fixed.
•
• Rotational constant B agrees well with theoretical predictions
• Lambda-doubling constant p+2q well determined– q held fixed, not defined (3) in
final fit
• Hyperfine splitting only observed in = 1/2 state– Only h1/2 and d1/2 could be
established
• Data analyzed to experimental accuracy of 50 kHz
mhfldsoroteffˆˆˆˆˆ HHHHH
Spectroscopic Analysis of CCPSpectroscopic Analysis of CCP
• Confirmed CCP linear molecule – More discussion of its structure next talk by M. Sun (FC03)
• With these rest frequencies, we found CCP in space– See talk FD07
• Many other interesting phosphorus species could be measured in the laboratory
Summary and Future WorkSummary and Future Work
• Lucy Ziurys
• Dennis Clouthier
• Emmy Tenenbaum
• Ming Sun
• Robin Pulliam
• Lindsay Zack
• Jessica Dodd
• Gilles Adande
• NASA Astrobiology Institute
• NSF Astronomy and Astrophysics Postdoctoral Fellowship
AcknowledgementsAcknowledgements