Post on 26-Dec-2015
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)26930 26931 26932 26933
26930.5 26930.6 26930.7 26930.8 26930.9 26931
cm-1
cm-1
dissociation
ISC
T1
fluo.
S0
phos.
IC
S1
abs.
IVR
S2
Vibronic Coupling (NBO)
Spin-orbitCoupling
Coriolis Coupling
Excited-state Dynamics
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
n
n nVV )cos1(2
1)(
CH3 Torsion of Toluene
Staggered Eclipsed
V3 = 0
V6(S0) = -4.874 cm-1
V6(S1) = -26.376 cm-1
D. R. Borst and D. W. Pratt, J. Chem. Phys. 113, 3658 (2000)
y(a)
z(b)x(c)
μ
Molecular Symmetry Group G12 (C3v×C2)
G12 is isomorphic to the D3h group.
0 100 200 300 400
0
100
200
300
V6 (cm-1)
Level Energy (cm-1)
6a1’
3a2”
3a1”
6a2’
0a1’
2e’1e”
4e’
5e”
7e”
Energy Levels of CH3 Torsion of Toluene or 9MA
.0
,2,1,0
6
2
Vwhen
m
FmE
2800028500
2700027500
CH3
Fluorescence Excitation Spectra in Supersonic Jets
000
000
cm-1
CH3
ψ50
ψ53
ψ47
HOMO
ψ48
LUMO
ψ49
ψ46
ψ52
LUMO
ψ51
HOMO
Molecular Orbitals and S1 - S0 Transition
Fluorescence Excitation Spectrum of 9MA
1. J. A. Syage, P. M. Felker, and A. H. Zewail, J. Chem. Phys. 82, 2896 (1985)
2. F. Tanaka, S. Hirayama, and K. Shobatatake, Bull. Chem. Soc. Jpn. 59, 2011 (1986)
3. Y. Stepanenko, A. L. Sobolewski, and A. Mordzinski, J. Mol.Spectrosc. 233, 15 (2005)
4. M. Nakagaki, E. Nishi, K. Sakota, H. Nakano,and H. Sekiya, Chem. Phys. In press.
27000275002800028500cm-1
Rotational envelopes
269252693026935cm-1
273102731527320cm-1
26985269902699527000cm-1
0a1’→ 3a1”0a1’→ 0a1’1e”→ 1e”
1e’→ 4e’
Assignments can be confirmed by OODR.
Fluorescence Excitation Spectrum of 9MA in a Supersonic Jet
Energy Levels of CH3 Torsion of 9MA
0 100 200 300 400
0
100
200
300
V6 (cm-1)
Level Energy (cm-1
)
6a1’
3a2”
3a1”
6a2’
0a1’
2e’1e”
4e’
5e”
7e”
40 cm-1
S1
105 cm-1
S0
0a1’→ 0a1’ 1e”→ 1e”← 0.8 cm-1 →
Energy Levels of CH3 Torsion of 9MA4e'3a1"
3a2"2e'1e"0a1' 0 cm-1
520
57
23
72S1
V6 = 40 cm-1
F = 5.2 cm-1
S0
4e'
3a1"
3a2"2e'1e"0a1'V6 = 105 cm-1 0 cm-1
41626
79
110
F = 5.2 cm-1
0 cm-14.3
1625
79
100
0 cm-15.1
2038
57
85
Calc.
Calc.
Barrier Height to CH3 Rotation (cm-1)
S0 -4.874 81 25
S1 -26.376 25 (V3) 10 (V6)
Barrier Height to CH3 Rotation (cm-1)
S0 ~105 73 ~0
S1 ~40 292 ~0
Single Vibronic Level Dispersed Fluorescence Spectrum of 9MA in a Supersonic Jet
IVR starts
at 388 cm-1.
Enhancement of IVR by CH3
J. B. Hopkins, D. E. Powers, and R. E. Smalley, J. Chem. Phys. 71, 3886 (1979)
IVR in Anthracene
W. R. Lambert, P. M. Felker, and A. H. Zewail, J. Chem. Phys. 81, 2209 (1984)
H. Ishikawa, Ph.D. Thesis, Kyoto Univ. 1993.
Rotational Structure of Vibronic Bands of Toluene
CH3 Torsion of Toluene
D. R. Borst and D. W. Pratt, J. Chem. Phys. 113, 3658 (2000)
UV
CW YVO4 LaserTi:Sapphire Ring Laser
PMT
PhotonCounter
Magnet
ΔE < 0.0001 cm-1
Computer
Millenia X CR899-29
Wavetrain
Pulse nozzle
Collimated Molecular Beam and Single-mode Laser
CH3
Ultrahigh-Resolution Spectrum of 0-0 Band
26930 26931 26932 26933
26930.5 26930.6 26930.7 26930.8 26930.9 26931
cm-1
cm-1
1e’’→1e’’
0a1’→ 0a1’
-3 -2 -1 0 1 2 3
-3 -2 -1 0 1 2 3
-3 -2 -1 0 1 2 3
Calculated Spectra of 9MAA-type
B-type
C-type
cm-1
26930 26932
9MAcalculation
experiment
cm-1
Rotation-torsion Hamiltonian
zFyxzF pPACPBPPA
VFpH
'2
)6cos1(2
1ˆ
222
62
yxzF
z
ICIBIIA
IIIF
2/,2/),(2/
/12/222
2
22
2)1(
2
|ˆ|
622 VFmmKAK
CBAJJ
CB
JKMmHJKMm
FF
0 0.1 0.2 0.3
H = 0T
H = 1.2T
9MA 0-0 Band
cm-1
Relative wavenumber
Ultrahigh-resolution Spectrum and Zeeman Effect
• 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.
CH3 Levels of 9MA and the Excited-state Dynamics