1. Dissociation Dynamics of Hydrogen-dihalogen Complexes Richard A. Loomis Washington University in St. Louis Department of Chemistry Abstract: WF12 – June 20, 2007 OSU 62 nd International Symposium on Molecular Spectroscopy

2. Spectroscopy of Dihalogen Complexes w/ T-shaped and Linear Conformers He n ···ICl Ne···ICl H 2 ···ICl D 2 ···ICl He n ···Br 2 He···I 2 Ne···I 2 Ar···I 2 H 2 ···I 2

3. Spectroscopy of H 2 ···ICl in the ICl B–X, v–0 spectral region I 2 P 3/2 + Cl 2 P 1/2 I + 3 P 2 + Cl – 1 S 2 I 2 P 3/2 + Cl 2 P 3/2 3.03.54.02.5 0 1000 2000 17500 41000 Transition Energy (cm –1 ) I–Cl Distance (Å) X 1+X 1+ B 3  0+ Z 1 B 0 + E 0+ 18000 39000 Pump ICl E  X Fluorescence Probe Vib. Pred. ICl B  X Fluorescence Laser-induced Fluorescence Action Spectroscopy

4. Assigning o,p-H 2 ···ICl Features (ICl B–X, 3–0 Region) * * * * * o-H 2 ···I 35 Cl * p-H 2 ···I 35 Cl  10 * ICl or He  ICl Features T-shaped (Asymmetric) Linear

5. Binding Energies of Different Conformers of the Dihalogen Complexes Partner in T-shaped Well Partner in Linear Well o-H 2 ···I 2 p-H 2 ···I 2 118.9(1.9) 91.3-93.3 102.7(9) -- He···ICl Ne···ICl 22.0(2) cm –1 16.6(3) cm –1 84(1) 70(5) o-H 2 ···ICl p-H 2 ···ICl 186.4(3) 82.8(3)-89.6(3) 156.8(1.3) 70(1)-77.9(3) p-D 2 ···ICl o-D 2 ···ICl 223.9(2.4) 97.3(8)-103.9(3) 202(3) 87.7(3)-95.2(2)

6. H 2 and ICl(X,v  =0) Electrostatic Potentials and Interactions -Gaussian 03 Linear Well C 2v Symm. Top T-shaped Well Asymmetric Dipole – Quad.Quad. – Quad.

7. Energies of Ground and Excited State H 2 ···I 35 Cl Levels C 2v, Prolate Symmetric Top Asymmetric Delocalized H 2 + I 35 Cl(X,v  =0) H 2 + I 35 Cl(B,v=3)

8. H 2 + I 35 Cl(B,v=3) Potential – scaled He + I 35 Cl(B,v=3) Potential Ray & McCoy (º)(º) R (Å) Minimum 135 cm –1

9. Localized H 2 ···I 35 Cl* Asymmetric States Ray & McCoy  (  ) R (Å) n=0 n s =0, n b =0 –81 cm –1 n=1 n s =0, n b =1 –59 cm –1 n=2 n s =0, n b =2 –49 cm –1

10. Delocalized H 2 ···I 35 Cl* States Ray & McCoy  (  ) R (Å) n=3 n s =0, n b =3 –44 cm –1 n=4 n s =0, n b =4 –41 cm –1 n=5 n s =0, n b =5 –38 cm –1

11. Stretchng H 2 ···I 35 Cl* States Ray & McCoy  (  ) R (Å) n=12 “n s =0, n b =12” –10 cm –1 n=13 “n s =1, n b =?” –9 cm –1 n=14 “n s =1, n b =?” –8 cm –1

12. Energies of Excited State H 2 ···I 35 Cl Levels Delocalized w/ Stretching Asymmetric Delocalized H 2 + I 35 Cl(B,v=3) Ray & McCoy

13. Adiabatic Potentials of H 2 + I 35 Cl(B,v=3) v str = 1 H 2 + I 35 Cl(B,v=3) Ray & McCoy 04080120160 –100 –80 –60 –40 –20 0  (  ) Energy (cm –1 ) v str = 0

14. Excited-State Dissociation Dynamics

15. H 2 in Linear Well H 2 in T-shaped Well H 2 –ICl Distance (Å) Energy (cm –1 ) H 2 (j) + ICl(X,v  =0) H 2 (j) + ICl(B,v–1, j) H 2 (j) + ICl(B,v–2, j ) H 2 (j) + ICl(B,v)

16. Rotational Contour of Lower Energy C 2v o-H 2 ···I 35 Cl Feature C 2v o-H 2 ···I 35 Cl

17. P5 Vibrational Predissociation of Asymmetric o-H 2 ···I 35 Cl(B,v=3,n=0) P10 P15 I 35 Cl E–B, 10–2

18. I 35 Cl(B,v=2) Rotational State Distribution Asymmetric o-H 2 ···I 35 Cl(B,v=3,n=0)

19. I 35 Cl(B,v=2) Rotational State Distribution Asymmetric p-H 2 ···I 35 Cl(B,v=3,n=0)

20. o-H 2 ···I 35 Cl(B,v=3,n=0) Vibrational Predissociation Dynamics R(Å) (º)(º) Rotational Rainbow low j high j E = –68 cm –1

21. I 35 Cl(B,v=2) Rotational State Distribution Delocalized o-H 2 ···I 35 Cl(B,v=3,n)

22. o-H 2 ···I 35 Cl(B,v=3,n=3) Vibrational Predissociation Dynamics R(Å) (º)(º) Rotational Rainbow from dissociation at Linear and Anti-Linear regions low j high j E = –46 cm –1 Predissociation of n=3 complexes forms sligthly colder ICl* distributions

23. D 2 ···ICl* Dissociation Dynamics D 2 in Linear Well D 2 in T-shaped Well H 2 –ICl Distance (Å) Energy (cm –1 ) D 2 (j) + ICl(X,v  =0) D 2 (j) + ICl(B,v–1, j) D 2 (j) + ICl(B,v–2, j ) D 2 (j) + ICl(B,v)

24. 1782017830178401785017860 T-shaped Fluorescence Intensity Wavenumbers (cm –1 ) Asymmetric Spectroscopy of D 2 ···ICl Complexes (ICl B–X, 3–0 Region) D 2 ···I 35 Cl He···I 35 Cl I 35 Cl

25. 1796017980180001802018040 C 2v, Prolate Symmetric Top Fluorescence Intensity Wavenumbers (cm –1 ) Spectroscopy of D 2 ···ICl Complexes (ICl B–X, 3–0 Region) D 2 ···I 35 Cl

26. H 2  I 35 Cl(B,v) Action Spectra Asymmetric p-D 2 ···I 35 Cl Asymmetric o,p-D 2 ···I 35 Cl(B,v=3,n=0) Features Asymmetric o-D 2 ···I 35 Cl

27. H 2  I 35 Cl(B,v) Vibrational Predissociation Dynamics

28. Acknowledgements: Dave Boucher Josh Darr John Glennon Andrew Crowther Dave Strasfeld

29. Acknowledgements: Ben McCall – University of Illinois

30. Acknowledgements: Anne McCoySara Ray

31. Acknowledgements: Funding The End Packard Foundation Washington University National Science Foundation ACS - PRF GAANN

32. The End

33. Rotational Contour of Lower Energy H 2 ···I 35 Cl Feature Asymmetric o-H 2 ···I 35 Cl B–X, 3–0

34. Assigning the Lower Energy Features (ICl B–X, 3–0 Region) Asymmetric o-H 2 ···I 35 Cl Asymmetric p-H 2 ···I 35 Cl

35. Possible H 2 ···ICl(X,v  =0) Structures ortho-H 2 (j  =1)para-H 2 (j  =0) C 2v Asymmetric

36. Assigning the H 2 ···I 35 Cl Features (ICl B–X, 3–0 Region) C 2v p-H 2 ···I 35 Cl Asymmetric o-H 2 ···I 35 Cl Asymmetric p-H 2 ···I 35 Cl C 2v o-H 2 ···I 35 Cl

37. Determining the C 2v, Prolate Symmetric Top H 2 ···ICl(X,v  =0) Binding Energy

38. C 2v, Prolate Symmetric Top Asymmetric H 2 –ICl Distance (Å) Energy (cm –1 ) H 2 + ICl(X,v  =0) H 2 + ICl(B,v=2) Pump Probe

39. ×1000 Determining the C 2v, Prolate Symmetric Top H 2 ···ICl(X,v  =0) Binding Energy H 2 ···I 35 Cl C 2v, Prolate Symmetric Top Continuum D 0  =186.4(3) cm –1

40. Determining the H 2 ···ICl(A,v) Binding Energy of the Asymmetric Conformer X 1  + Pump Probe A 3  1 I 2 P 3/2 + Cl 2 P 3/2

41. H 2 + ICl(X,v  =0) H 2 + ICl(A,v=21) H 2 + ICl(A,v=22) H 2 + ICl(A,v=20)  v = –2 Vib. Prediss.  v = –1 Vib. Prediss. Pump Determining the H 2 ···ICl(A,v) Binding Energy of the Asymmetric Conformer

42. v=24  v = –2  v = –1 p-H 2 ···ICl v=23v=21 o-H 2 ···ICl o-H 2 ···ICl v=22 p-H 2 ···ICl

43. The spectroscopic shifts of the complexes from the monomers can then be used to bracket the ground state binding energies –o-H 2 ···I 35 Cl(X,v  =0) 82.8(3)  D 0  89.6(3) cm –1 Determining the H 2 ···ICl(X,v  =0) Binding Energy of the Asymmetric Conformer The observed vibrational distributions place limits on the binding energy of the excited state complexes –o-H 2 ···I 35 Cl(A,v=21) D 0  82.9 cm –1 –o-H 2 ···I 35 Cl(A,v=22) D 0  74.9 cm –1

44. 69.5(3)-76.3(3) 59.4(1.0)-67.3(3) o-H 2 ···ICl(B,v=3) p-H 2 ···ICl(B,v=3) Summary of H 2 ···I 35 Cl Binding Energies AsymmetricC 2v Sym. Top o-H 2 ···ICl(X,v  =0) p-H 2 ···ICl(X,v  =0) 186.4(3) 82.8(3)-89.6(3) 156.8(1.3) 70.0(1.0)-77.9(3)

45. Action Spectroscopy of H 2 ···ICl Complexes (ICl B–X, 3–0 Region)

46. 178001785017900179501800018050 C 2v, Prolate Symmetric Top Fluorescence Intensity Wavenumbers (cm –1 ) Asymmetric Spectroscopy of D 2 ···ICl Complexes (ICl B–X, 3–0 Region) D 2 ···I 35 Cl

47. Determining the C 2v, Prolate Symmetric Top H 2 ···I 2 (X) Binding Energy

48. Acknowledgements Prof. Loomis, Dave Boucher, John Glennon, Andrew Crowther, and other previous group members Prof. Anne McCoy, OSU Prof. Ben McCall, Univ. of Illinois Prof. Lev Gelb, Washington Univ.

49. Assigning o,p-(H 2 ) 1 ···ICl Features Asymmetric H 2 ···I 35 Cl C 2v p-H 2 ···I 35 Cl C 2v o-H 2 ···I 35 Cl

50. Bond lengths at this level of theory: –H 2 : 0.743 Å (0.741 Å exp.) –ICl: 2.346 Å (2.319 Å exp.) H 2 and ICl(X,v  =0) Electrostatic Potential Calculations Calculation performed on Gaussian 03 with CCSD optimized structures –H and Cl atom basis set: aug-cc-tzp –I atom basis set: SDB-cc-tzp

51. Action Spectroscopy of H 2 ···ICl Complexes (ICl A–X, 21–0 Region)

52. ×100 Ro-vibronic Spectra of H 2 ···ICl Complexes (ICl B–X, 2–0 and 3–0 Region) * * * * I2I2 * * * * I 35 Cl B–X, 2–0 I 35 Cl B–X, 3–0 * ICl or He  ICl Features T-shaped Linear * * * LIF Action

53. Action Spectra of H 2 ···ICl Complexes (ICl B–X, 3–0 Region) * * * ICl or He  ICl Features * T-shaped Linear

54. Interactions of o,p-H 2 + ICl H 2 in Linear Well H 2 in T-shaped Well H 2 –ICl Distance (Å) Energy (cm –1 ) p-H 2 (j=0) + ICl(X,v  =0) p-H 2 (j=0) + ICl(B,v=2) o-H 2 (j=1) + ICl(X,v  =0) o-H 2 (j=1) + ICl(B,v=2)

55. Determining the H 2 ···ICl(X,v  =0) Binding Energies Action spectroscopy performed by probing the direct dissociation pathway used to determine the linear, ground-state binding energies Closing of vibrational predissociation product- state distributions and anharmonicity of ICl(B) used to bracket the excited-state binding energies Spectral shifts in excitation spectra and excited- state binding energies are used to bracket the T-shaped, ground-state binding energies

56. p-H 2 ···ICl(X,v  =0)  o-H 2 ···ICl(X,v  =0) Conversion * * * A/B = 5.2 Action Spectra in the I 35 Cl B–X, 3–0 Region A/B = 28.8 A o-H 2  ICl p-H 2  ICl B * ICl or He  ICl Features Conversion w/ collisions and excess H 2