Electron energy loss studies of Cl2using a position-sensitive multidetector electron spectrometer

Abstract
An electron spectrometer which incorporates a position-sensitive detector and differential pumping has been used to obtain spectra of molecular chlorine up to the second ionisation potential A 2 Pi u. This is the first experimental work to reveal transitions above 11.3 eV and the first using electron impact to produce spectra with a scattering angle as high as 90 degrees . The best energy resolution displayed in the present spectra is 18 meV (FWHM) which is significantly better than any previously reported. Features which are forbidden by electric-dipole selection rules are discerned by obtaining spectra using a variety of scattering conditions. Many previously reported transitions are seen plus approximately seventy new ones, some of which combine to form three Rydberg progressions and eight new vibrational series. Five of these series are allowed by electric-dipole selection rules and three are spin forbidden.