Photoelectron spectroscopy of C3Si and C4Si2 anions

The 364 nm photoelectron spectra of the linear C3Si- and C4Si2- anions are reported. Accurate adiabatic electron affinities are determined: EA((3)Sigm a C3Si)=2.827 +/-0.007 eV and EA(C4Si2)=2.543 +/-0.006 eV. Several vibratio nal frequencies for both neutral molecules are also obtained. The term ener gy for the first linear excited state of C3Si (either (1)Delta or (1)Sigma) is 0.274 +/-0.015 eV. For C4Si2, the term energy is substantially lower th an in C3Si and vibronic interactions between the two states become stronger . Experimental results are compared with high-level ab initio calculations for C3Si (see Rintelman and Gordon, following paper) and with our own calcu lations for C4Si2 and its anion. (C) 2001 American Institute of Physics.