Photoelectron spectroscopy of As-, As-2(-), As-3(-), As-4(-), and As-5(-)

The negative ion photoelectron spectra of As-,-As-2, As-3(-), As-4(-), and As-5(-) have been measured. From these, the electron affinities of As, As-2 , As-3, As-4, and As-5 have been determined to be 0.814, 0.739, 1.45, <0.8, and similar to 1.7 eV, respectively. In the case of As-2(-), the following molecular constants were also determined: r(e)(As-2(-))= 2.239 Angstrom, o mega(e)(As-2(-)) = 293 cm(-1), omega(e)chi(e)(As-2(-)) = 4.9 cm(-1), D-0(As -2(-)) = 3.89 eV, and Delta E[(2)Pi(g)(3/2)-(2)Pi(g)(1/2)] = 0.256 eV. In t he case of As-3(-), vertical detachment energy (VDE) was measured to be 1.6 2 eV, and for As-3, Delta E((2)A(2)-B-2(1)) was determined to be 0.36 eV. F or As-4(-), VDE was found to be 1.52 eV. The relatively high stability of A s; suggests that it, like Pg,may be a candidate for forming cluster-assembl ed, ionic crystals of stoichiometry, MAs5, where M is an alkali metal atom. Similiarities with other small cluster anions of Group V elements are also discussed. (C) 1998 American Institute of Physics. [S0021-9606(98)00748-X] .