EXPERIMENTAL AND ABINITIO STUDIES OF ELECTRONIC-STRUCTURES OF THE CCL3 RADICAL AND CATION

The structures and optical spectroscopy of the CCl3 radical and cation were studied by ab jnitio molecular orbital calculations and by experiment. The structures of the X1A1′ (D3h) state of the CCl3 cation and the X2A1(C3v) and X2A2″ (D3h) structures of the CCl3 radical were optimized by ab initio calculations using the 6-31G* basis set. The optimized structure of the CCl3 cation is a D3h structure with re(C-Cl) = 1.6437 Å. The ground state of the CC13 radical is of X2A1 (C3v) symmetry with re(C-Cl) = 1.7142 Å and ∠(Cl-C-Cl) = 117.10°. Vibrational frequencies for each CCl3 species were computed. The electronic spectrum of C35Cl3 radicals was observed between 336 and 440 nm using mass resolved resonance enhanced multiphoton ionization (REMPI) spectroscopy. This spectrum arose from two-photon resonances with planar Rydberg states. A third laser photon ionized the radicals. One Rydberg series of quantum defect δ= 0.545 is comprised of the Ē 2E′ (3p) state (v0-0 = 47 170 cm-1, ω1(a1′ sym str) = 544 (6) cm-1, ω2′(a2″OPLA) = 509 (21) cm-1, spin-orbit splitting = 33(5) cm-1) and the K 2E′ (4p) state (v0-0 = 56236 cm-1, ω2′ = 526 (16) cm-1). A second Rydberg series of δ= 0.50 is comprised of the F 2A2″ (3p) state (v0-0 = 47868 cm-1, ω2′ = 528(3) cm-1) and the L 2A2″ (4p) state (v0-0 = 56409 cm-1, ω2′ = 533 (15) cm-1). A third Rydberg series (δ= 0.216) was comprised of the G (3d) (v0-0 = 51 218 cm-1, ω2′ = 520 (17) cm-1) and M (4d) (v0-0 = 57733 cm-1, ω2′ = 542 (3) cm-1) states. A fit of the Rydberg formula to these series found the adiabatic ionization potential of the CCl3 radical to be IPa = 8.109 (5) eV. The J 2A1′ (4s) Rydberg state (v0-0 = 53 471 cm-1, ω2′ = 530 (20) cm-1) was also observed. The REMPI spectrum exhibited the v2″ = 1-4 vibrational hot bands of the X 2A1 (C3v) radical. Modeling of these hot bands derived the inversion barrier, Binv = 460 ± 40 cm-1. © 1990, American Chemical Society. All rights reserved.