Dietmar Panten

Electronic absorption spectra of CCS− and CCS in neon matrices

Mass selected C2Sions have been co-deposited with neon to grow a matrix at 6 K. The A 2 R þ X 2 P and B 2 P X 2 P elec- tronic absorption spectra of the linear CCSanion have been identified with origin band at 10 606 and 22 273 cm � 1 , respectively. After exposure to UV radiation a new electronic transitionðE 3 RX 3 R � Þ of CCS is observed (origin band at 30 563 cm � 1 )i n addition to its known A 3 P X 3 Rband system. Ab initio calculations provide support for the symmetry assignment of the upper electronic states of CCS � , CCS and of the vibrational structure in the spectra.

Rovibronic states of the X2Π state of CCO

Abstract For the X 2 Π electronic ground state of CCO− three-dimensional potential energy functions have been generated ab initio and used in variational Renner–Teller calculations including electron spin. The spin–orbit constant has been calculated to be −57.8 cm−1, the rotational constant Be=0.3831 cm−1, with ReCO=1.221 A and reCC=1.308 A. Rovibronic levels (J=P) for J⩽5/2 are given for energies up to about 4000 cm−1. For the vertical A 2 Σ + –X 2 Π transition the electronic transition moment amounts to 0.88 debye, yielding a radiative lifetime of 1.1 μs for the A-state.

A theoretical study of the Renner–Teller effect in the X̃2Πg state of C3−

Abstract Three-dimensional potential energy functions for the A ″ and A ′ components of the X 2 Π g state of C 3 − have been generated ab initio using the internally contracted multi-reference configuration interaction method. The spin–orbit constant in this state has been calculated from a complete-active-space-self-consistent-field wavefunction. These data were used to solve the linear/linear Renner–Teller problem variationally for J = 1/2, 3/2 and 5/2. Rovibronic levels for K =0, 1 and 2 were determined for energies up to about 3800 cm −1 . The very large splitting between A ″ and A ′ was found to give rise to a strong mixing for the rovibronic Π and Δ bending states. The results are compared with those obtained experimentally and for similar molecular systems.

Rovibronic States in the X2Π State of the CCS− Anion

Abstract Three-dimensional potential energy functions have been generated ab initio for the X2Π electronic ground state of CCS− and used in variational Renner–Teller calculations including electron spin. Rovibronic levels (J=P) for J≤5/2 are given for energies up to 4000cm−1. The pattern of the levels is compared with that of CCO−. In the case of CCS− the quartic force fields, equilibrium geometry, electric dipole moment, the electronic affinity and the Franck–Condon factors for the X2Π(CCS−) → X3Σ− (CCS) photodetachment spectrum are calculated.