/ AD-AlSO 863 NATIONAL B3UREAU OF STANDARDS WASHINGTON DC NATIONAL M-ETC F/6 7/4I TRIPLY DIFFERENTIAL STUDIES OF ATOMIC AND MOLECULAR PHOTOIONIZA--ETC(U)IJUL 81 J L DEHMCR, A C PARR, R STOCKBAUER N00018B1-F0005

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PEA, INSTRUCV JSREPORT DOCUMENTATION PAGE IIEFORECOIPLET! C FOR

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4. TITLE 'e~d Svb!:Ie A.-N"1~ IRPORT a vrPton COVEfIE.)triply Differential Studies of Atomic and M.'olecular Surmrmary QuestionnairosewsPhotoionization Using Synchrotron Radiationv / 1 June 1880-30 Scpt 1q81,

P!RPONG. REPORT NUME -1

7. AUTHOR(.) 8. CONTRACT OR GRANT N~jM9FR'-)

I.L. Dehrner (Argonne National Laboratory) /- N00014-- 8l-F-0005A. C. ParrR. Stockbauer _____________

9. PERFORMING ORGA.-OZATION NAME AND A00RESS 10. PROSPAV -- ,EMEN. PRS.E-T. TA%-C

National Meoasurement Laboratory AREA & -04K UNIT NUMBERS

1-4 National Bureau of Standards NR 393-051S Washington, D.C. 20234 _____________

11. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

=1 Office of Naval Research 6 July 1981-r_ Physics Program Office . 13. NUMBERV PAGES

ArinIc l i-re-inii 19917OF, MNTRNr AGECNCY NAME a AOORESS(ef different from Conttrolling OI!jc8) 5SEjTYCAS(othaaei

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SCmEDULE

W6 DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.,,

4U-VISTRIBUTION STATEMENT (of the abstract enteredIff Block 20. If different from Report)

18. SUPPLEMENTARY NOTES

IS KEY WORDS (Continue on reverse side )l necessary and identify by block rnumber)l

SPhotoicnkation * atoms, molecules, branchinig ratio, photoeiectror. spectroscopy,5. photoelectron angular distribution, synchrotron radiation, autoiOnization,

C) shape resonance, atomic clusters, photoelectron-photoion coincidence,C-.) fluorescence polarization.

L.J 20 ABSTRACT (Contirne an reverse aide If necessary and Identify by bto'.k rnumber)

Basic studies of the dynamics and spectroscopy of atomic and molecular phoDto-LA. ionization have been carried out using three experimantal probes. The firstS and most extensively used experimentel approach involves triply diffurentia-'

(differential in incident wavelength, electron energy, and ciection anglo) photzI-electron measurements using synchrotron radiation. DMeasurernznts woreconducted in the vacuum ultraviolet w,-avelength range up to h,, r 35 cV on

DID 14 73 EDI TION OF I NOV 65 IS OBSOLETE UnclassifiedSIN 102LF-14-601SECURITY CLASSIFICATION4 OF THIS PAGE (01ten Data E..Ipd)

81701fO-~

UnclassifiedSECURITY CLAI.F tCATION4 OF THIS PAG

e (1flhelm Dsta £nt1e4l

20 (contd). several atomic and molecular species, e.g., Ar, Kr, Xe, H 2 , N2 ,02, CO, S02, C2H2. C2N2 , HCN, CH 3 CN, BF 3 , and SF 6. Photoelectronbranching ratios and angular distributions were obtained for all accessible states.A major emphasis of this work involved the initial exploration of novel effectsof autoionization and shape resonances on alternative vibrational ionizationchannels. The second experimental approach entailed measuring the polarizationof fluorescence following production of excited molecular ions by photoionization.This was also a novel experiment, allowing the direct measurement of thealignment of molecular ions produced by photoionization and, simultaneously,the branching ratios for degenerate photoelectron channels. The third experl-mental approach was, again, a novel experiment, and involved determining thephotoelectron spectrum of an atomic cluster (Xe 3 ) in a mixture of clustersformed in a supersonic expansion by the technique of photoion-photoelectroncoincidence.

UnclassifiedSECURITY CLASSIFICATION OF THIS PAGENOjen D ,S P nero'd

SUMMARY QUESTION:;AIR

Triply Differentiil Studies of Atomic and Mdolecular PhotoionizationUsing Synchrotron Radiation (Contract No. N00014-81-F-0005)

Submitted to

Office of Naval ResearchPhysical Sciences Division

Physics Program OfficeDepartment of Navy

Arlington, VA 22217

ATTN: Dr. Bobby R. Junker

Submitted by

National Bureau of Standards6 July 1981

Accession For

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1. Principal Investigators:

J. L. Dehr-er, Senior PhysicistArgonne National Laboratory

Argonne, ILL 60439

Tel: 312-972-4194

Albert C. ParrSynchrotron Ultraviolet Radiation Facility

National Bureau of StandardsWashington, D.C. 20234

Tel: 301-921-2031

Roger StockbauerSurface Science Division

National Bureau of Standards

Washington, D.C. 20234Tel: 301-921-2096

2. Contract Description

The research covered by this contract involves basic studies of photoionizationprocesses in atoms and molecules using three novel and/or advanced experimentalapproaches outlined in item 4. Topics of main interest include photoelectronbranching ratios, photoelectron angular distributions, alignment of molecular ionsby photoionization, and photoelectron spectra of atomic clusters.

3. Scientific Problem

This study is aimed at resolving roughly four unknown or incompletely knownaspects of this problem area: First, this program seeks to ch,-racterize' majoraspects of photoionization dynamics, such as the effects of shape resonances and Iautolonizing resonances on alternative ionization channels, which can only nowbe studied in a definitive way with the advanced techniquut employed in this work.Second, we seek to develop new probes of the photoionization process, e.g.,fluorescence polarization spectroscopy and photoelectron spectroscopy of atomicclusters, which will yield new types of information. Third, this project producesdata crucial to testing theoretical predictions and, thus, contributes to thedevelopment of realistic theories of atomic and molecular photolonization. Fourth,the data produced by this project contributes to characterizing all the pathwaysby which radiation interacts with matter, and hence contributes to the macroscopicmodeling of such interactions.

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4. Scientific and Technical Approach

This program utilizes three experimental approtichos: First, the main effortinvolves measuring triply differential photoelectron cross sections usingsynchrotron radiation. Thus the intensity of photoelectrons ejected from atcmsand molecules are measured as a function of three independent parameters - thewavelength of the incident synchrotron radiation, the kinetic energy of thephotoelectron, and the ejection angle relative to the polarization direction of thelight. Second, the polarization of fluorescence from excited ionic states producedby photoionization is measured as a function of the wavelength of the incidentlight. Third, photoelectron spectra are measured in coincidence with the massof the ion produced in order to obtain the photoelectron spectra of specific atomicclusters in the presence of a whole range of clusters formed in a supersonicexpansion.

S. Progress

Triply differential measurements were conducted in the vacuum ultraviolet wave-length range up to hv \, 35 eV on several atomic and molecular species, e.g.,Ar, Kr, Xe, H2 , N2 , 02, CO, S02, C2112 , C2N2 , HCN, CH 3CN, BF 3, and SF 6.Photoelectron branching ratios and angular distributions were obtained for allaccessible states. A major emphasis of this work involved the initial explorationof novel effects of autoionization and shape resonances on alternative vibrationalionization channels. Protot~ype fluorescence polarization spectroscopy measurementswere perfopmed on theoB22.u state of NJ formed by photoionization of N 2 in therango 450 A < X < 660 A. The feasibility and theoretical interpretation of thisnew cl,iss of experimental probe was estdblished. Finally, in the third part of theproject, the photoelectron spectrum of 'Xc3 :s determined by photoelectron-phot )ion

coincidence technique using a supersonic jet source of xenon clusters.

6. Publications

The papers, abstracts of contributed talks, and invited talks are listed on thefollowing pages.

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PAPERS

1. B. E. Cok e, D. 1L. Ederer, 111. Stoch1'b:,utcr, K. Codling, A. C. Parr, J. 13. Weust,1. D. !'uaikoff, anid L 1. Dchmer, "'V ZirC11L1i anid Vifbract!01xia-StittDependonca of Photoolect~-ori Angular Distributions. Resonancc Effects in5a Photoio,)rh-.,tion of CO,"J Chern. Phys. 72, 6308 (1980).

2. A. C. Pairr, D. L. Ederer, B. E. Cole, J. B. WestL, Rt. Stockbaucer, K. Codlirrcj,and J. L. Dehmrer, "Triply -Differentia, Photoele('ctron Studies of MolecularAutolo ni'zation Profiles," Phys. Rev. Letters 46, 22 (1981).

3. E. D. Poli-akoff, J. L. Dehmeor, D. Dill, A. C. Parr, K. I-1. Jackson, andR. N. Zare, "Polarization of Fluorescence Followving Molecular Photoionization,"Phys. Rev. Letters 46, 907 (1981) .

4. K. Codling, A. C. Parr, D. L. Ederer, Rt. Stockbauer, J. B. West, B. E. Cole,and J. L. Debmer, "The Effects of AutoljOnization onl Vibrational BranchingRatios and Photoelectron Angular D-istributions in Moleculai Photolorilzation:

+ 0The Formation of the Ground State of 0~ Between 574 A and 600 A ."1. Phys. B 14, 657 (1981). 2

5. D. L. Ederer, A. C. Parr, B. E. Cole, Rt. Stockbauer, J. L. Dehmer, J. B.West, and K. Codling, "Vibrational-State Dependence of Partial Cross Sectionsand Pho'teelectron Angular Distributions through Autolonizing Resonances:The n =3 Rydberg Level Converging to the B 2 E+ State of CO-t, " Proc.Roy. Soc. (London), in press.

6. A. C. Parr, G. Rakowsky, D. L. Ederor, R. L. Stockbiuer, J. B. West, andJ. L. Dehrner, "Current Research at NBS Using Synchrotron Rad-i-ation atSURF-II,"1 IEEE Transactions on Nuclear Science, Volume NS28, in press.

7. J. B. West, K. Codling, A. C. Parr, D. L. Ederer, B. E. Cole, R. Stockbauer,and J. L. Dehmer. "Partial Photolonization Cross Sections and PhotoelectronAngular Distributions through the Hopufield Pands In,, N 2 Between 650 A and730 . ,"1 J. Phys. B, accepted for publication.

8.K. Codling, J. B. West, A. C. Parr, J. L. Dohmrer, and Rt. L. Stockbaiier."Measurement of Values and Branching Ratios In thle Region of the 3s3p6 p

1 Resonance in Ar and the 5s5p 6p lPo Resonance in Xe," J. Phys. B 13,L693 (1980).

9. E. D. Poliakoff, P. M. Dehmer, J. L. Dehmer, and R. L. Stockbauer, "ThePhotoelectron Spectrum of Xe 3 by the Photoclectron-Photoion CoincidenceTechnique," J. Chem. Phys. , accepted for plibl~cation.

ABSTRACTS OF CONTRIBUTED PAPERS

1. A. C. Parr, Jf. L, Dohmer, 1B. E. Colo, I). L. Edorer, R. L. Stocl:biuer, andI. B. West, "An Angle-Resol-vcd Photoeloc~tron Spectrometer for Triply-Differential Photolonization Studies, " Sixth Inturnational Conference onVacuum Ultraviolet Radiation Physics, June 2-6, 1980, Charlottesville, VA.Book of Extended Abstracts, p. 111-70.

2. K. Codling, J. B. West, A. C. Parr, J. L. Dehlner, B. E. Cole, D. L. Ederer,and R. L. Stockbauer, "Partial Cross SecLions, Vibrational Branching Ratios,and Angular Distributions in the 570-600 Window Resonance in 02," ibid.p. 11-14.

3. R. Stockbauer, A. C. Parr, J. L. Dehmer, B. E. Cole, D. L. Ederer, J. B. West,and K. Codling, "Perturbation of Vibrational Intensities and Angular Distributiosby Autoionization of Molecular PhotoionizZtion," ibid., p. H-15.

4. E. D. Poliakoff, J. L. Dehmer, A. C. Parr, D. Dill, K. H. Jackson, an,R. N. Zare, "Polarized Fluorescence Excta:b,, Spectroscopy of N2 , " ibid.p. 11-25.

5. J. L. Dehmer, A. C. Parr, J. B. West, K. Codling, D. L. Ederer, B. E. Cole,E. D. Poliakoff, and R. Stockbauer, "Ef,, cts of Shape Resonances onVibrational £ "nching Ratio-, and Pho'toelectron Angular Distributions in MolecularPhotoionization," ibid., p. 11-86.

6. A. C. Parr, R. L. Stockbauer, K. Codling, J. B. West, and J. L. Dehiner,"Photoelectron Branching Ratios and Angular Distributions in the Region ofthe 3s3p 6 4p ]Po Resonance in Ar and the 5sSp 6p 'PC Resonance in Xe,"Annual DEAP eeting, 1-3 December 1980, Los Angeles, CA, Bull. Am. Phys.Soc. 25, 1131 (1980).

7. J. L. Dehmer, J. B. West, K. Codling, R. Stockbauer, A. C. Parr, D. L.Ederer, and B. E. Cole, "Triply-Differential Photoionization Studies ofMolecular Autoionization Profiles," ibid., p. 13 .

8. E. D. Poliakoff, J. L. Dehmer, D. Dill, A. C. Parr, K. H. Jackson, andR. N. Zare, "Polarization of Fluorescence Following Molecular Photojonization,"ibid., p. 1136.

9. K. Codling, If. B. West, A. C. Parr, J. L. Dehmer, and R. L. Stockbauer,"Photoelectron Angular Distribution Measurements through AutoionizingResonances in Argon and Xenon," Molecular Spectroscopy and Dynamics withSynchrotron Radiation-A European Workshop, Maria Laach, West Germany,29 September-I October 1980, Book of Abstracts, p. 52.

10. R. Stockbauer, A. C. Parr, B. E. Cole, D. L. Ederer, J. Dehrmer, J. West,and K. Codling, "Effects of Two-Electron Resonances on Photoelectron Ernergyand Angular Distributions," presented orally at the Gordon Research Conflurnceon Electron Spectroscopy, Wolfsboro, Nil, July 1980 (no abstract available).

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ABSTRACTS OF CONTRIBUTED PAPERS (CONTINUED)

11. A. C. Parr, D. L. Ederer, R. Stockbuer, J. B. West, K. Codling, D.M.P.Holland, and J. L. Dehmer, "Triply-Difforential Photoelectron Stoducs ofAtomic and Molecular Phototonization," Twelfth Internutional Conference onthe Physics of Electronic and Atomic Collisions, 15-21 July 1981, Gatlinburg,Tennessee, Book of Abstracts.

12. E. D. Poliakoff, P. M. Dehmer, J. L. Dehnier, and R. Stockbauer, "ThePhotoelectron Spectrum of Xe 3 by the Phooalectron-Photoion CoincidenceTechnique," ibid.

13. E. D. Poliakoff, J. L. Dehmer, D. Dill, A. C. Parr, K. H. Jackson, andR. N. Zare, "Polarization of Fluorescence Following Molecular Photoionization,ibid.

14. A. C. Parr, D. L. Ederer, J. West, j. L. Deh-ner, "Resonance Effects in theAngular Distribution and Branching Ratios of the Photoelectrons in C2H2 andC2N2 , "' Annual Meeting of the American Society for Mass Spectrometry andAllied Topics, 25-29 May 1981, Minneapolis, inn., Book: of Abstracts.

15. D.M.P. Holland, A. C. Parr, D. Ederer, J. L. Dehmer, and J. B. West,"The Angular Distribution Parameters of Se!ected Rare Gases for Use inCalibration of Electron Spectrometers," National Synchrotron InstrumentationConference, Cornell University, 15-17 July 1981, Book of Abstracts.

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INVITED TALKS

1. J. L. Debmor and Dan Dill, "Shape Re nani-ccs in Molcculcir PI otoionizat ion,"Plenairy talk presonted aL Molecular Spcoctroscopy and Dynamnic-. withSynclirotiorn Radiation-A European WVorlksh1op, Maria Lacich, West Germany,September 29-October 1, 1980, Book: of Abstracts, p. '13.

2. A. C. Parr, "Current Research at NBS Using Synchr-otron Radiation atSURF-If,"1 Invited talk presented at the Si-th Conference on the Applicationof Acce-lzerators in Research and Ind:Iustry, Denton, TX, November 3-5, 1980.See paper 6.

3. J. L. Debmer, "Potpourri of Current and Future Studies of MolecularPhotoionization-Synchrotroni Radiation, Su.Lp ornc jets, and MultiphotonIonization,"1 Chemistry Department ClounBoston University, Boston, MA,13 Apri1 1981.

4. E. D. Poliakoff, "Two Novel Probes of Vc'_cular Photolo niza tion: Photoelectron-Photoion Coincidence Spectroscopy of Ato-mic Clusters and Fluor-esconce Polai-ization Analysis, " Atomic and Molecular Science Somin,-r, Argonne, NationalLaboratory, Argonne, Illinois, 6 M11ay, 19".

S. A. C. Parr, "Resoniance Phenomena in olcua Photoianization," MolecularSpectroscopy Division Seminar, Nationa1 Burcu of' Standa.rds, Gaithersburg,MD, 21 May 1981.

6. E. D. Poliakoff, "Alignment of Mlolecul-ir Ions Prod uced by Photoionization,"Seminar on Collision Experiments in The_-ir T er Fia ratin (Fcano Workshop)),The University of Chicago, Chicago, IL, 23 Mliy 1981.

7. A. C. Parr, "Status of Programns at NBS SUR_,F-Il,"1 National SynchrotronInstrumentation Conference, Cornell University, 15-17 July 1981.

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7. Extenuating Circumstances

None.

8. Unspent Funds

None will remain unspent at the end of the current contract period.

9. Graduate Students Receiving Degrees

None.

10. Other Federal Contract Support

J. L. Dehmer is a co-principal investigator of Office of Naval ResearchContract N00014-81-F-0051, "Selectivity of Multiphoton Processes,"6/1/81 - 5/31/82.

R. Stockbauer is a co-principal investigator of Office of Naval ResearchContract NOO14-81-FO021, "Characterization of Surface Bonding Using Photonand Electrol Simulated Desorption", I Oct 1980 - 30 Sept 1931.

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