UV photoelectron spectra have been recorded for the F + NH20H reaction at different reaction times. At short reaction times three bands associated with NH,O were observed, whereas at longer reaction times one band associated with NHO was seen.The NH20 bands were assigned with the aid of ab initio molecular orbital calculations which used an essentially planar equilibrium geometry for the neutral ground state. The HNO band showed resolved vibrational structure which was analysed in terms of excitation of the N-0 stretching and HNO deformation modes in HNO+(g 2A'). The first adiabatic and vertical ionization energies of HNO(g 'A') were measured as 10.18 & 0.01 and 10.56 0.01 eV, respectively. Assignment of the vibrational structure was confirmed by recording the first photoelectron band of DNO, prepared from the F + ND20D reaction.
The title reactions have been investigated in the gas phase using UV photoelectron spectroscopy. By recording spectra at different reaction times, it was possible to detect reaction intermediates and hence identify pathways by which each reaction proceeds. The F2 + CH3SCH3 reaction appears to proceed via the intermediate CH3-SFCH3 whereas the F2 + CH3SSCH3 reaction gives H2CS and HF as the first observed products. For both reactions at longer reaction times, a new spectrum associated with a reaction product, consisting of three photoelectron bands with adiabatic ionization energies of 10.15 f 0.01, 11.49 f 0.02, and 13.71 0.01 eV, has been observed. This spectrum is assigned to the HFCS molecule. The first two adiabatic ionization energies of HFCS have been calculated using the Gaussian-2 (G2) theoretical procedure as 10.09 and 1 1.5 1 eV, respectively, supporting this assignment. This work represents the first observation and spectroscopic study of this molecule. A broad band with a vertical ionization energy of 10.58 f 0.06 eV, assigned to the first ionization energy of HCF, has also been observed as a secondary product from both reactions under conditions of excess F2 partial pressure. This assignment is supported by first adiabatic and vertical ionization energies of HCF computed at the G2 level of theory. For each reaction, a reaction mechanism is proposed on the basis of the results obtained.
Recent developments in the use of photoelectron spectroscopy to study reactive intermediates in the gas phase are reviewed. The information to be derived on low-lying cationic states from such studies is illustrated by considering two diatomic molecules, NCI and PF, and one triatomic molecule, HNO. Also, the use of a transition-metal photoelectron spectrum to interpret the photoelectron spectrum of the corresponding transition-metal oxide is discussed by using the spectra of vanadium and vanadium monoxide as examples. The value of super-heating in high-temperature photoelectron spectroscopy is demonstrated by considering the vapour-phase photoelectron spectra of the monomers and dimers of sodium hydroxide.
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