Characterization of C_4H in the A~2 and X~2 states by double resonance four-wave mixing

摘要

The B~2 - X~2 electronic spectrum of C_4H has been studied by degenerate and double resonance four-wave mixing. The technique identifies vibrational levels in the X~2 ground state. Its sensitivity and unique characteristics permit detection of new levels. The A~2 state lying 222 cm~(-1) above the X~2 ground state is also observed, confirming the analysis from anion photoelectron spectroscopy but with improved accuracy. Vibrational level determination in the A~2 electronic manifold up to 700 cm~(-1) above v 0 is made. A Renner-Teller analysis is carried out for the two lowest bending modes v _6 and v_7 in the A~2 state by diagonalization of the effective Hamiltonian matrix. The Renner-Teller parameters _(6, 7), and ε_(67), the vibrations ε_6 and ε_7 and the spin-orbit coupling constant Aso are determined.