1. Slow electron velocity mapping for the study of cationic states of aromatic molecules CHIH-HSUAN CHANG ¥, GARY V. LOPEZ ¶, PHILIP M. JOHNSON ¶,and TREVOR J. SEARS ¥,¶ ¥ Department of Chemistry, Brookhaven National Laboratory, Upton, New York 11973; ¶ Department of Chemistry, Stony Brook, Stony Brook University, New York 11794

2. Introduction Aromatic molecule are benchmark systems for gas phase study. The substituted group in phenyl structure plays an important role in the spectroscopy and molecular dynamics, such as internal rotation, intersystem crossing, and internal conversion. The interaction of the  electron between the phenyl ring and substituting group. styrene benzaldehydephenylacetylene toluene

3.  electron molecular orbitals of benzene, toluene, PA, and styrene  2,3  4,5 11 66

4. Absorption spectrum of phenylacetylene G. W. King and S. P. So, J. Mol. Spectrosc.37 543(1971)

5. Molecular orbital transition and electronic configuration 35% 1 B 2 state: 37%(L+1  H)+38%(L  H-1) 1 A 1 state: 81%(L  H) 1 A 1 state:76%(L+1  H-1) Serrano-Andres et al. J. Chem.Phys 119,4294(2003)

6. Experimental philosophy for slow electron velocity mapping S0S0 S1S1 D0D0 IP  2 =0.46(3)  2 =0.79(6) 1+1 REMPI scheme 1+1’ REMPI scheme 1 1 1 2 F.C. factor

7. The S 1  S 0 absorption spectrum of jet-cooled PA by 1+1 REMPI 8 8 7 1 2 34 15[ 36 ]:phenyl CCH,C 7 C 8 H 8 bend 10b[ 24 ]:out of plane ring def, C 7 C 8 H 8 bend 6a[ 12 ]: C 7 C 8 H 8 － ring breath βCC[ 35 ]: C 1 C 7 H 8 bend βCH[ 33 ]:C 7 C 8 H 8 bend 6b[ 34 ]: Ring deform 1[ 12 ]: ring breath

8. The vibrational levels of phenylacetylene in the S 1 state Symmetry Our result 15 1 b2b2 146 10b 2 a1a1 194 10b 2 15 1 b2b2 337 6a16a1 a1a1 409  CC 1 b2b2 493 10b 1 6a 1 b1b1 516 6b16b1 b2b2 555  CH 1 b2b2 561  CC 1 15 1 a1a1 639 1 a1a1 719 6a26a2 a1a1 821  CC 1 6a 1 b2b2 902 12 1 a1a1 945 18a 1 a1a1 954  CC 2 a1a1 917 9a19a1 a1a1 1152 13 1 a1a1 1191  CC 1 1 1 b2b2 1208 6a36a3 a1a1 1229 6b 1 1 1 b2b2 1271  CC 1 12 1 b2b2 1436 1212 a1a1 1442  CC 1 9a 1 a1a1 1463 18a 1 6b 1 b2b2 1529  CC 1 9a 1 b2b2 1641 1 1 12 1 a1a1 1660  CC 1 13 1 b2b2 1682 13 1 6b 1 b2b2 1754 18a 2 a1a1 1908 CC 1 a1a1 2013

9. The vibrational levels of phenylacetylene cation in the D 0 state via transition of selected levels in the S 1 state

10. Vibrational level Vib symmetry Kwon et al.Lin and TzengDyke et al. S 1 state 0 15 1 10b 2 10b 2 15 1 6a 1  CC 1 6a 1 10b 1  CH 1 6b 11 15 1 b2b2 154150143 10b 2 a1a1 223221 10b 1 15 1 a2a2 257 16a 1 a2a2 346 10b 2 15 1 b2b2 361 6a16a1 a1a1 458453449458439460  CC 1 b2b2 480499 6b16b1 b2b2 572564561560 6a 1 10b 1 a2a2 578 15 1  CC 1 a1a1 648 6a 1 10b 2 a1a1 685657 1 a1a1 748766747759 6a 1 10b 2 15 1 b2b2 822 6a26a2 a1a1 914910904913914921 6a 1  CC 1 b2b2 939 1 1 10b 2 a1a1 976 6a 2 10b 1 b1b1 10141019 6a16b16a16b1 b2b2 10441024 6a 2 10b 2 a1a1 1107 6b26b2 a1a1 1116 6a 1  CH 1 b2b2 1119 6a 2 15 2 a1a1 1185 116a1116a1 a1a1 12161205 1 1  CC 1 b2b2 12441246  CC 1 10a 1d b1b1 1287 116b1116b1 b2b2 13251319 6a36a3 a1a1 13751387136913701372 6a 2  CC 1 b2b2 1407 6a 1 12 1 a1a1 1437 6a 2 6b 1 b2b2 14711474 6a 3 10b 1 b1b1 1475 12 1  CC 1 b2b2 14731465 1212 a1a1 1514 6b 1 12 1 b2b2 15171538 6a 1 10b 1 12 1 b1b1 1542 6a 3 10b 2 a1a1 1563 6a 2 6b 1 10b 1 a1a1 1629 116a2116a2 a1a1 1668 1 1 12 1 a1a1 1734 126a1126a1 a1a1 1940 1 1 13 1 a1a1 1994 Summary of vibrational frequencies and their assignment for phenylacetylene in the cation ground state

11. Angular distribution of electron ionized via different vibration modes Θ e-e- ε For a linearly polarized light the angular distribution has the general form:

12. Summary of the results of PA with SEVM detection With 1+1 REMPI and slow electron velocity mapping (SEVM) detection, the vibrational structure of S 1 and D 0 states of the phenylacetylene were determined, as well as the photoelectron angular distribution. Vibronic coupling with 1 A 1 state is enhanced by  CC in-plane mode. The 6a, phenyl ring breathing motion, is an active mode in the cation state. The angular distribution of photoelectron provides vibronic coupling information.