VELOCITY MAP IMAGING STUDIES OF NON-CONVENTIONAL METHANETHIOL PHOTOCHEMISTRY Ben Toulson, Jon Alaniz & Craig Murray Examples of non-conventional photochemical mechanism: R. D. van Zee et al., J. Chem. Phys., 1993, 99, 1664 A. Suits et al., Acc. Chem. Res. 2008, 41, 873 H 2 CO CO (v = 0, j =15, 28, 40) + H 2 (v,j) j CO = 40 j CO = 28 j CO = 15 A. Suits, J. Bowman et al., Science, 2004, 306, (5699), 1158 Others: NO 3, acetaldehyde 3+1 REMPI of NH via D 3 X 3 transition NH + ion signal /arb. S 1 T 1 J. Thomas et al., J. Phys. Chem. Lett., 2012, 3, IC ~ 0.24 cm -1 k ISC ~ 0.6 x10 9 s -1 k pr ~ 2.6 x10 12 s -1 CH 3 NH 2 : Roaming-mediated intersystem crossing? CH 3 SH photodissociation CH 3 SH + h CH 3 S + H H = 3.73 eV CH 3 + SH H = 3.08 eV CH 4 + S( 3 P J, 1 D 2 ) G. Vaghjiani. J. Chem. Phys., 1993, 99, 5936 New primary photoproduct? E. Jensen et al., J. Chem. Phys., 1993, 98, 2882 Velocity map imaging correlated properties of photofragment distributions (internal energy, anisotropy) S. Greaves, R. Rose, A.J. Orr-Ewing, Phys. Chem. Chem. Phys. 2010, 12, 9129 R. Livingstone et al. J. Chem. Phys. 2012,137, vv time-of-flight Sulfur 2+1 REMPI, photolysis = 235 nm 3PJ3PJ 1D21D2 wavelength / nm CH 3 S photodissociation? / nm 3P2:3P1:3P03P2:3P1:3P a 51:35: a 57:30:13 a. H. Bise et al., J. Chem. Phys. 110, 805 (1999) b. This work CH 3 S + h pump CH 3 + S( 3 P J ) + h probe CH 3 + S( 3 P J ) / nm 3P2:3P1:3P03P2:3P1:3P0 Average ( ) a 88:6: a 15:42:43 No evidence currently suggests that CH 3 S absorbs at pump or probe S( 1 D 2 ) observed: inconsistent with CH 3 S photodissociation CH 3 SH + h S( 3 P J ) photolysis = 235 nm 1D21D2 3P23P2 2 pump 2 probe 11 2 pump 2 probe 11 Conclusion & future work Complementary roles for theory and experiment Roaming-mediated intersystem crossing in CH 3 NH 2 ? Trends and generalized behaviors in CH 3 SH, CH 3 NH 2 Prof. Craig Murray Jonathan Alaniz Liz Hargreaves Catherine Adams Acknowledgements S( 3 P J ) photoproducts, photolysis = 235 nm 3P13P1 3P03P0 3P23P2