Sergey I. Panov

VIBRATIONAL SPECTROSCOPY OF THE CHLOROBENZENE CATION USING ZERO KINETIC ENERGY PHOTOELECTRON SPECTROSCOPY

The one‐color (1+1) resonance‐enhanced multiphoton ionization (REMPI) spectrum of the S1(1B2) state of chlorobenzene has been recorded and is similar to that obtained by other workers. Zero‐kinetic‐energy (ZEKE) photoelectron spectroscopy was then used to probe the vibrational levels in the ground electronic state of the cation (I+0) using a two‐color photoionization scheme via the S1 electronic state. By using different intermediate vibrational levels in the S1 state, different vibrations could be accessed in the ion. Vibrational symmetry selection rules for the I+0←S1 ionization appear to hold well. Exciting through different S1 vibrational levels has revealed the probable mixing of the S1 normal coordinates in I+0. A previously‐identified Fermi resonance in the S1 state is also confirmed by the ZEKE spectra. The adiabatic ionization energy is measured as 73 170±5 cm−1.

THE ELECTRONIC SPECTROSCOPY OF THE BA+-AR COMPLEX : POTENTIAL SURFACE AND DISSOCIATION ENERGIES

Ba+–Ar open‐shell ionic complexes were produced in a pulsed free‐jet expansion. The dispersed emission and both the low and high resolution A 2Π–X 2Σ+ excitation spectra of the Ba+–Ar complex are reported. The data obtained were used to construct potentials for the ground and excited states. A simple quantum mechanical model was introduced in order to simulate the experimentally measured potentials. The model potential is used to estimate the dissociation energy of the ground 2Σ+ state. This value, when combined with the spectral red shift, allows the dissociation energies of the two components of the excited 2Π state to be determined. The same electrostatic interaction model also explains the observed angular momentum coupling scheme as well as the much stronger binding in the excited 2Π state.

The spectroscopy of the CdCH3 radical and its positive ion

Resonantly enhanced multiphoton ionization, REMPI (2 color, 1+1′), and zero electron kinetic energy-pulsed field ionization, ZEKE-PFI, spectra are reported for the first organometallic radical, CdCH3. The combined REMPI and ZEKE-PFI data have necessitated a change of assignment for one of the bands of the A2E←X 2A1 electronic transition of the neutral radical. The new assignment and the revised molecular parameters are reported. The ZEKE-PFI spectrum yields the adiabatic ionization potential for the CdCH3 radical and four of the six possible vibrational frequencies of its cation. Clearly resolved rotational (K level) structure is observed in some bands of the ZEKE-PFI spectrum, providing a unique experimental test for newly extended ZEKE-PFI rotational selection rules.