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One-photon mass-analyzed threshold ionization (MATI) spectrum of trans-[C.sub.2][H.sub.2][Cl.sub.2] is obtained by using vacuum ultraviolet radiation generated by four-wave mixing in Kr. The spectrum has displayed abundant overtones and combinations and the equilibrium geometry of the cation is estimated through the Franck-Condon fit.

An investigation of the production of C7H7+ in the unimolecular and photoinduced dissociation of ethylbenzene, methylcyclo-heptatriene and o-, m- and p-xylene ions, using mass-analyzed ion kinetic energy spectrometry is made. This investigation shows an interesting trend of increasing benzylium production with the increase in the total number of carbon atoms in the alkyl substituents.

A consistent and improved method for the Whitten-Rabinovitch (WR) approximation employed in the semi-classical computation of the Rice-Ramsperger-Kassel-Marcus (RRKM) unimolecular reaction rate constant is presented for application to protein reactions. The method proved to be better than the WR calculations method or the Beyer-Swinehart (BS) method and also the RRKM rate constant can be computed instantly without considering the protein mass.

A study of vinyl chloride cation in the first excited electronic state using vacuum ultraviolet radiation in the range of 107 - 102.8 nm obtained by one photon mass-analyzed threshold ionization spectroscopy is presented. The spectral resolution achieved in the study is insufficient to determine the lifetime of the state and hence an experimental method is being researched to confirm the very long lifetime of this action state.

C2H335Clin the ground vibronic state was generated by one-photon mass-analyzed threshold ionization spectrometry, and its photodissociation in the 461−406 nm range was investigated. Ionization energy to the ground state of C2H335Clwas 10.0062 ± 0.0006 eV while its state onset was higher by 2.7456 ± 0.0003 eV. A vibrational spectrum of the cation in the state obtained by recording the product ion yield as a function of wavelength was analyzed by referring to the quantum chemical results at the TDDFT/B3LYP/6-311(df,pd) level. Analysis of product time-of-flight profiles recorded with different laser polarization angles showed that the dissociation pathway for the cation in the state changed with the vibrational energy, from internal conversion to and statistical dissociation therein to curve crossing to and repulsive dissociation therein. → curve crossing seemed to occur along a direction close to the C−Cl bond stretch. [ABSTRACT FROM AUTHOR]

Vibrational spectrum of vinyl chloride cation in the first excited electronic state, Ã2A‘, was obtained by one-photon mass-analyzed threshold ionization (MATI) spectroscopy. Use of an improved vacuum ultraviolet radiation source based on four-wave sum frequency mixing in Hg resulted in excellent sensitivity for the MATI signals. From the MATI spectrum, the ionization energy to the Ã2A‘ state of the cation was determined to be 11.6667 ± 0.0006 eV. Nearly complete vibrational assignment for the MATI peaks was possible by utilizing the vibrational frequencies and Franck−Condon factors calculated at the DFT and TDDFT/B3LYP levels with the 6-311G(3df,3pd) basis set. Geometry of the cation in the Ã2A‘ state was determined by Franck−Condon fitting of the MATI spectrum. [ABSTRACT FROM AUTHOR]

Examines the photodissociation dynamics of conformers of iodobutane isomer ions. Use of ion cyclotron resonance mass spectrometry; Identification of the photoelectron spectra of iodobutane isomers; Protonation of the methylcyclopropane.