Electronic excitation and oscillator strength of ethyl bromide by vacuum ultraviolet photoabsorption and electron energy loss spectroscopy

The high resolution vacuum ultraviolet photoabsorption spectrum of ethyl bromide has been recorded between 5 and 10.15 eV (248-122 nm) using synchrotron radiation. It exhibits a broad structureless valence band centred at 6.1 eV of low cross section followed by a region dominated by excitation of Rydberg states. A high resolution photoelectron spectrum (PES) of the lowest energy ionization band has been obtained and provides ionization energies necessary for identification of related Rydberg-excited states. Also, analysis of the vibrational fine structure in the PES has allowed identification of the normal vibrational modes excited and their wave numbers in the ion. These data, in turn, have been used in the assignment of the lowest energy photoabsorption bands arising from electron excitation into the 5s Rydberg orbital. The electron energy loss spectrum, recorded from 6.5 to 14.1 eV, under electric-dipole conditions, confirms the magnitude of the photoabsorption cross-section values obtained using the synchrotron radiation and extends the differential and optical oscillator strength values up to 14.004 eV. (C) 2000 American Institute of Physics. [S0021-9606(00)01814-6].