1. Methyl Torsional Levels in 9-Methylanthracene
Masaaki Baba (Kyoto Univ. Japan)
Yuki Noma (Kyoto Univ. Japan) Shunji Kasahara (Kobe Univ. Japan)
Takaya Yamanaka (IMS, Japan)
Jon T. Hougen (NIST, Gaithersburg)

2. Excited-state Dynamics
dissociation
ISC T1
fluo. S0
phos. IC S1
abs.
IVR S2
Vibronic Coupling (NBO)
Spin-orbit
Coupling
Coriolis Coupling
Excited-state Dynamics

3. CH3 Internal Rotation (Torsion)
How large is the barrier height V3 and V6 ?
Enhancement of radiationless transitions.
¶ Density Increment of coupling levels
¶ Vibrational mixing including out-of-plane modes

4. CH3 Torsion of Toluene V3 = 0 V6(S0) = -4.874 cm-1
Staggered
Eclipsed
D. R. Borst and D. W. Pratt, J. Chem. Phys. 113, 3658 (2000)

5. Molecular Symmetry Group G12 (C3v×C2)
z(b)
x(c) μ
y(a)
G12　is isomorphic to the D3h group.

6. Energy Levels of CH3 Torsion of Toluene or 9MA

7. Fluorescence Excitation Spectra in Supersonic Jets
000
000
CH3
cm-1

8. Molecular Orbitals and S1 - S0 Transition
CH3
ψ53
ψ49
ψ52
LUMO
ψ48
LUMO
ψ51
HOMO
ψ47
HOMO
ψ46
ψ50

9. Fluorescence Excitation Spectrum of 9MA
J. A. Syage, P. M. Felker, and A. H. Zewail, J. Chem. Phys. 82, 2896 (1985)
F. Tanaka, S. Hirayama, and K. Shobatatake, Bull. Chem. Soc. Jpn. 59, 2011 (1986)
Y. Stepanenko, A. L. Sobolewski, and A. Mordzinski, J. Mol.Spectrosc. 233, 15 (2005)
M. Nakagaki, E. Nishi, K. Sakota, H. Nakano,and H. Sekiya, Chem. Phys. In press.

10. Rotational envelopes
0a1’→ 0a1’
1e”→ 1e”
1e’→ 4e’
0a1’→ 3a1”

11. Assignments can be confirmed by OODR.

12. Fluorescence Excitation Spectrum of 9MA in a Supersonic Jet

13. Energy Levels of CH3 Torsion of 9MA
100
200
300
400 V 6
(cm -1 )
Level Energy (cm
6a1’
3a2”
3a1”
6a2’
0a1’
2e’
1e”
4e’
5e”
7e”
40 cm-1 S1
105 cm-1 S0

14. Energy Levels of CH3 Torsion of 9MA
Calc.
4e'
3a1"
3a2"
2e'
1e"
0a1'
0 cm-1 5 20 57 23 72 S1
V6 = 40 cm-1
F = 5.2 cm-1 85 57 38 20
5.1
0 cm-1
0a1’→ 0a1’
1e”→ 1e”
← cm-1 →
Calc.
4e'
0 cm-1 4 16 26 79
110
0 cm-1
4.3 16 25 79
100 S0
3a1"
3a2"
F = 5.2 cm-1
2e'
1e"
V6 = 105 cm-1
0a1'

15. Barrier Height to CH3 Rotation (cm-1)S
S (V3) (V6)

16. Barrier Height to CH3 Rotation (cm-1)
S ~ ~0
S ~ ~0

17. Single Vibronic Level Dispersed Fluorescence Spectrum of 9MA in a Supersonic Jet
IVR starts
at 388 cm-1.

18. Enhancement of IVR by CH3
J. B. Hopkins, D. E. Powers, and R. E. Smalley, J. Chem. Phys. 71, 3886 (1979)

19. IVR in Anthracene
W. R. Lambert, P. M. Felker, and A. H. Zewail, J. Chem. Phys. 81, 2209 (1984)

20. Rotational Structure of Vibronic Bands of Toluene
H. Ishikawa, Ph.D. Thesis, Kyoto Univ

21. CH3 Torsion of Toluene
D. R. Borst and D. W. Pratt, J. Chem. Phys. 113, 3658 (2000)

22. Collimated Molecular Beam and Single-mode Laser
Ti:Sapphire
Ring Laser
CW YVO4 Laser
Millenia X
CR899-29
ΔE < cm-1
Wavetrain
Magnet
Computer
Pulse nozzle
Photon
Counter UV
PMT

23. Ultrahigh-Resolution Spectrum of 0-0 Band
CH3
0a1’→ 0a1’
1e’’→1e’’

24. Calculated Spectra of 9MA
A-type
B-type
C-type
cm-1

25. 9MA
calculation
experiment
cm-1

26. Rotation-torsion Hamiltonian

27. Ultrahigh-resolution Spectrum and Zeeman Effect

28. CH3 Levels of 9MA and the Excited-state Dynamics
The potential barrier to rotation (V6) is estimated to be 110 (S0)and 40 (S1) cm-1, which is higher than that in toluene.
The transition energy of 1e”→ 1e” is larger than 0a1’→ 0a1’ by 0.8 cm-1.
IVR take places at the vibronic levels higher than 388 cm-1.
The interaction with the triplet state is weak.