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A new method is proposed for the measurement of translational energy distributions in which a species with three energy levels is excited by two successive transitions with perpendicular laser beams. Simulations of the method are carried out for the photodissociation of H2 O and a pilot experiment was performed on Li atoms dissociated from LiI vapor. [ABSTRACT FROM AUTHOR]

The photodissociation of ethylene at 193 nm is studied by laser induced fluorescence of the hydrogen atom product. The quantum yield for producing deuterium atoms from C2D4 is 0.19±0.04. Their average translational energy is 7.3±1.3 and 15.1±1.4 kcal/mol at 193 and 157 nm, respectively. Considerable evidence, both experimental and theoretical, shows that dissociation takes place from a hot internally equilibrated ground state molecule. A remarkable isotope effect is found. The ratio of H atoms to D atoms released from CH2CD2 is 2.2±0.2, whereas that from t-CHDCHD is 1.2±0.1. An RRKM model explains these ratios. For CH2CD2 the vibrational frequencies of the transition state for releasing H atoms are quite different from those for the release of D atoms. In t-CHDCHD, the transition state frequencies are nearly the same; there is a cancellation between differing zero point energies and moments of inertia. [ABSTRACT FROM AUTHOR]

The absorption and fluorescence excitation spectra of jet cooled Cd(CH3)2 and Cd(CD3)2 were measured in the structured region between 230 and 200 nm. The symmetric Cd–methyl stretch and methyl umbrella modes in the second excited electronic state of the latter molecule were found to the 304 and 790 cm-1, respectively. Widths of the 0–0 lines (FWHM) were 101 and 25 cm-1, respectively from which lifetimes of 53 and 265 fs were deduced. A weak fluorescence due to CdCH3 is excited by the absorption of Cd(CH3)2 and an even weaker fluorescence is excited in Cd(CD3)2. The quantum yield of this fluorescence is below 10-4 at the electronic origin of the structured band and increases to about 10-3 above 2000 cm-1 vibrational energy. [ABSTRACT FROM AUTHOR]