Fate of excited states in jet-cooled aromatic molecules: bifurcating pathways and very long lived species from the S1 excitation of phenylacetylene and benzonitrile.
Pump-probe delayed ionization studies on phenylacetylene and benzonitrile in a supersonic beam reveal the production of a low-ionization-potential (approximately 5.7 eV) species lasting more than hundreds of microseconds after excitation to the S1 state. Excitation of the molecules was done with a frequency-doubled, Fourier transform-limited, pulse-amplified cw laser, and the rotationally resolved structure of the S1-S0 transition ensures that the excited molecules are monomers. Excited-state photoelectron spectroscopy shows that the long-lived species are formed during the light pulse but not by transfer from the fluorescing S1 population after the pulse, even though the S1 spectral signature is present in the long-lived action spectrum. This behavior differs greatly from that found in benzene and with most commonly held pictures of radiationless transitions in large molecules.
Hofstein
Jason
J
Department of Chemistry, Stony Brook University, Stony Brook, New York 11794-3400, USA.
Xu
Haifeng
H
Sears
Trevor
T
Johnson
Philip
P