Ultraviolet photoelectron spectroscopy of the unstable molecules ClSeCN and BrSeCN and the stable Se(CN)₂

Broken symmetry effects in the He(I) valence photoelectron spectrum of Se(CN)2

“…However, application of the HFS scheme to Se(CN)a assuming a C~v symmetry constraint predicted an order of spectral bands which is at variance with the experimentally preferred assignment [29]. This behaviour was rather unexpected in view of the good agreement between experiment and HFS-calculated spectra within a C~ symmetry constraint for the related compounds SeC12 and SeBr~ [33].…”

“…In figure 1 the PE spectrum of Se(CN)2 is reproduced together with the preferred experimental assignment. Further details can again be found in [29].…”

“…For a theoretical interpretation of the PE spectra of small molecules the Hartree-Fock-Slater (HFS) quantum chemical computation scheme has been shown to be very reliable for an extensive series of compounds [29][30][31][32][33][34]. However, application of the HFS scheme to Se(CN)a assuming a C~v symmetry constraint predicted an order of spectral bands which is at variance with the experimentally preferred assignment [29].…”

“…Although an accurate experimental geometry for Se(CN)~ is not available, a reasonable estimate for its structure could be derived from a comparison with related molecules. For experimental and geometrical details we refer to a previous paper [29].…”

“…The STF exponents were obtained by least squares fitting an LCAO expansion for each atomic orbital to an accurate numerical solution of the atomic HFS equations [36]. For the calculations on Se(CN)2 one d polarization function is added to the selenium basis set [29].…”