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David H. Parker Radboud University Nijmegen 3–5 February, 2015 Leiden 1.

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Presentation on theme: "David H. Parker Radboud University Nijmegen 3–5 February, 2015 Leiden 1."— Presentation transcript:

1 David H. Parker Radboud University Nijmegen 3–5 February, 2015 Leiden 1

2 Dr. Gautam Sarma Chandan Bishwakarma VUV Photodissociation RET in CO collisions DAN members Zhongfa SunRoy Scheidsbach CW-TOP project “Imaging Astrochemistry” Prof. Arthur Suits (USA) “Radboud Excellence” program VUV photodissociation RET in CO collisions VMI of ice surfaces with H. Cuppen, S. Ioppolo, J. Bouwman, H. Linnartz Polarization dependent DCSs

3 branching ratios » Measure branching ratios of all major channels in photodissociation of relevant molecules over the nm region » Controlled conditions (clusters, rotation, vibration, electronic excitation, collisions, …) 3 3–5 February, 2015 Leiden

4 4

5 » PE Curves:  states » Parallel or perpendicular TDMs » Axial recoil? » Correlation diagrams as starting point for dissociation dynamics 5 3–5 February, 2015 Leiden   E k’ E   k’ D1D0D1D0 recoil:

6 a)Monomer with cold internal states b)Photodissociation over full VUV c)Probes for all channels COS ( 1 A’) + h  CO X 1  v, J) + S( 1 S) CS A 1  (v,J) + O( 1 D) 6 3–5 February, 2015 Leiden Angle-Speed distribution of state-selected products Angle-Speed distribution of state-selected products a)Cold molecular beam b)VUV photodissociation c)Photoionization d)Velocity Mapping Lens e)Imaging detector f)Camera Needed:

7 1 3  u state » cross section » dissociation products  minor channel  test of theory 7 3–5 February, 2015 Leiden D1D0D1D0 ?

8 Universal Ionization Mass Spectrometer h O2O2 h  or e - J. Lin D. Hwang, YT Lee, XM Yang JCP (1998) : : I (D 1 ) II (D 0 ) Previous Work

9 9 B3u-13u1u5u23u+B3u-13u1u5u23u+ 3–5 February, 2015 Leiden  u 1  u 5  u 2 3  u + B3u-B3u- Theory Balakrishnan, Jamieson, Dalgarno, Li, Buenker JCP 112, 1255 (2000)

10 Product atom  D 1 Branching D 1 (x )  D 0 Branching D 0 (x ) O( 3 P 2 )2 ± ± ± ± 0.1 O( 3 P 1 ) O( 3 P 0 ) Average 3 P0.9 ± 0.3 O( 1 D 2 )2 ( 1 F det)1.0± % M J =0 Ix20 O 157 nm O( 3 P 1 ) D nm D 0 D nm E laser O 2 dissociation at 157 nm

11 3–5 February, 2015 Leiden 11 undercounting Sub-pixel Event Counting / Centroiding

12 Ratio (B 3  u - ):(1 3  u ) = 2:1 Branching and betas are consistent with curve crossing from the B 3  u - state to the 5  u and 1  u states However, beta for O 3 P 0 is <2. Mix between sudden and adiabatic limit 3u3u 1u1u 5u5u 3u+3u+ 1/3 2/3 Partial correlation diagram

13 146.3 nm 3x cm 2 2x10 -3 of  B-X

14 Log(Intensity) 157 D 0 – positive  146 D 0 – negative 

15 Product atom  D 1 Branching D 1 (x (157 nm))  D 0 Branching D 0 (x ) O( 3 P 2 )2 ± ± ± O( 3 P 1 ) O( 3 P 0 ) Average 3 P O( 1 D 2 )2 ± 0.05M J =0 Ix20 D nm E laser O 2 dissociation at 146 nm D nm D 0 O 146 nm O( 3 P 2 )

16 cm 2 157nm from Lewis (x15) 146 nm B ~2x stronger 146 nm 157 nm x6 total B3u-B3u- 13u13u

17 1.Secondary dissociation becomes possible 2.Interaction potential  2 bond lengths + 1 angle 3.>100 rovibrational channels for CO 4.Nonlinear molecule: TDM mixed 5.Non-axial recoil affected by vibrational motion 6.Conical intersections, seams, etc. 7.Full quantum theory to long R not possible 8.Competition with photodissociation by ICR, IC, ISC. 17 3–5 February, 2015 Leiden

18 Absorption Spectrum  motion parallel E. Heller, Ann Rev Phys Chem 1986

19 VUV absorption spectra of OCS by Vaida static and jet-cooled Position of origin band? jet cooledRoom temperature

20 3–5 February, 2015 Leiden 20 COS (X 1 A’) + h  CO X 1  v, J) + S( 1 S) CS A 1  (v,J) + O( 1 D) CO X 1  v, J) nm  CO A 1   LIF S( 1 S) nm  S( 3 D°)  LIF Major Channel

21 nm  x cm 2 PHOFEX Peak at 157 nm disappears in Phofex spectrum!

22

23 Detection of S( 1 S) atoms S( 3 P) CO +S( 1 D) S( 3 D°) COS LIF nm 219 nm 20 ns

24 157nm accidentally resonant with autoionizing resonance of S( 1 S)

25  (cm 2 ) S( 1 S) autoionization cross section nm  x cm 2 F 2 laser McGuire PRA (1979) PHOFEX

26 S( 3 P) CO +S( 1 D) S( 3 D°) COS LIF nm 219 nm detection of S( 1 S) atoms S+S+ Autoionization ~157 nm S( 1 D) 20 ns same laser pulse

27 3–5 February, 2015 Leiden 27 COS (X 1 A’) + h  CO X 1  v, J) + S( 1 S) CS A 1  (v,J) + O( 1 D) CO X 1  v, J) nm  CO A 1   LIF S( 1 S) nm  S( 3 D°)  LIF Major Channel CO X 1  v, J) nm  CO A 1  nm  CO +

28 28 3–5 February, 2015 Leiden CO, CO 2 and COS in the VUV x 10 3 cm -1

29 8.00 eV CO 2 I.P. = eV CO I.P. = eV CO(X) CO(A) CO + (X) 155 nm I.P. CO nm nm 155nm CO(X)+O( 1 D) 7.42 eV CO(X) +O( 3 P) D eV Xe

30 Prof. Arthur Suits (Wayne State, USA)

31 31 3–5 February, 2015 Leiden S. H. Gardiner, L.Lipciuc, C. Vallance, T. Karsili and M. N. R. Ashfold, Phys. Chem. Chem. Phys., 2014, DOI: /C4CP04654D

32 3–5 February, 2015 Leiden 32  Highly sensitive and informative method  Steps towards full nm scans » O 2 – deviation from theory for weak channels » COS – PHOFEX-LIF S atoms, non-axial recoil » CO 2 – strong polarization, smoother » CH 3 OH – clusters, CH 3 images 118 nm detection (see Ashfold paper on CH 3 I!)


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