Electron affinities of Si, Ge, Sn and Pt by tunable laser photodetachment studies

The electron affinities of silicon, germanium, tin and platinum are measured by tunable laser photodetachment spectroscopy via detection of the neutral atomic species. The binding energy values obtained for Si-, Ge- and Sn- (electron configuration np(3) with n = 3 to 5) are 11207.0(5) cm(-1), 9942.6(4) cm(-1) and 8969.6(5) cm(-1), respectively. The improvements in accuracy over the existing values in the literature for these three species lie between one and two orders of magnitude. The binding energy of the 5d(9)6s(2) D-2(5/2) ground level of Pt- is found to be 17141(6) cm(-1). This result is in relatively good agreement with the two existing results in the literature. Finally, the prospects for further studies of atomic negative ions are briefly discussed.