Conformer selective and vibrationally mediated photodissociation dynamics of propanal cation

Lei Shen, Myunghwa Kim, Bailin Zhang, Arthur G. Suits

Department of Chemistry, Wayne State University

Geometric optimization of propanal cation (C3H6O+)

cis conformer (0.07o) gauche conformer (118.9o)

Gauche form is more stable and energy difference is only about 65 cm-1 in the lowest ionic state with the barrier height, 344 cm-1.

Cis form is more stable in both the ground and Rydberg states of neutral propanal.

The geometry optimization was performed with B3LYP/6-311++G** by Gaussian 03.

Two-photon spectroscopy of the 3s n Rydberg transition of propanal

J. Pfab, et al., J. Chem. Soc., Faraday Trans., 1997, 93, 2883

841 cm-1

Photoionization of propanal by (2 + 1) REMPI

I.P=9.999 (0.003)

I.P=9.944

M. H. Kim, L. Shen, A. G. Suits, Phys. Chem. Chem. Phys. 8, 2933-2939 (2006)

Photofragment (C3H5O+) images from the vibrationally and conformationally mediated photodissociation of propanal cation

cis origin (53943.9 cm-1) cis 151 (54146.0 cm-1) cis 152 (54349.6 cm-1) cis 153 (54554.8 cm-1)

gauche origin (54785.3 cm-1) cis 81 (55085.2 cm-1) cis 61 (55307.2 cm-1)cis 154 (54758.8 cm-1)

Conformer specific photodissociation of propanal cation

Cis

Gauche

Total Translational Energy (eV)

Potential energy diagram for C3H6O+

M. H. Kim, L. Shen, HL. Tao, T. J. Martinez, A. G. Suits. Science, 315, 1561-1565 (2007)

Dynamics on the D2 state

AIMS (ab initio multiple spawning)

Dynamics on the dark state (D1)

Deuterated result

CH3CD2CHO+ CH3CD2CO+ + H

H loss:

CH3CDCDHO+ CH3CDCDO+ + H

D loss:

CH3CD2CHO+

CH3CDCDHO+ CH3CDCHO+ + D

HL. Tao, L. Shen, M. H. Kim, A. G. Suits, T. J. Martinez (in preparation)

Reaction rates on the ground state

RRKM simulations:

Dynamics on the ground state

MOLPRO CAS (5/5)-PT2/6-31G**

Photofragment images (C3H5O+) with vibrational excitation

1123

1124

2223

2224

11

102315 1

1102415 1

1202315

11

202415

Mode selective photodissociation dynamics

3.30 3.35 3.40 3.45 3.50 3.55 3.60 3.6510

15

20

25

30

35

40

45

61 0

91 0

101 0

71 0/111 0

81 0

ga

uch

e

152 02

32 2

152 02

42 2

154 0

151 02

32 21

52 0231 1

153 0

152 02

41 1

151 02

42 2

151 02

31 11

52 0

232 2

151 02

41 1242 2

231 1

151 0

241 1

cis

Ave

rag

e r

atio

(fa

st/

tota

l) %

Total available energy (eV)

Acknowledgements

Wayne State: Stanford:

Prof. Arthur G. Suits Prof. Todd J. Martinez

Hongli Tao

Prof. Myung Hwa Kim

Dr. Bailin Zhang