Journal of Physical Chemistry, Vol.99, No.6, 1760-1767, 1995
Direct Identification of Photofragment Structures Formed in the 193-nm Photodissociation of Thiophene
An experimental scheme which involves vacuum ultraviolet photoionization mass spectrometric sampling of laser photodissociation products in a pulsed supersonic molecular beam has been used to identify the isomeric structures of the 193 nm photofragments from thiophene. The primary products observed are vinylacetylene (H2C=CH-C=CH), acetylene (C2H2), and thioketene (H2C=C=S). Using the 2 + 1 resonance-enhanced multiphoton (REMPI) scheme, we find that S atoms are produced predominantly (greater than or equal to 96%) in P-3(J) states with a fine structure distribution of P-3(2):P-3(1):P-3(0) = 0.82 +/- 0.03:0.15 +/- 0.03:0.03 +/- 0.03. These experimental results indicate that the major dissociation channels are CH2=CH-C=CH + S(P-3) and CH=CH + CH2=C=S. Ab initio multiconfiguration self-consistent-field calculations have been made to rationalize these experimental observations.
Keywords:GAS-PHASE;DEWAR THIOPHENE;SULFUR-ATOMS;FURAN;CS2;PHOTOIONIZATION;DISSOCIATION;IONIZATION;CLUSTERS;SINDO1