Experimental characterization of the higher vibrationally excited states of HCO+: determination of omega(2), x(22),, g(22), and b(030)

Analyses of high Rydberg series of HCO converging to the (030) vibrational state of the cation establish rovibrational state-detailed thresholds for H CO+. UV-visible laser double resonance isolates series for assignment. Stro ngly vertical Rydberg-Rydberg transitions from photoselected N' = 0 and N' = 2 rotational levels of the Sigma(-) Renner-Teller vibronic component of t he 3p pi (2)Pi (030) complex define individual series converging to rotatio nal levels, N' = 1 through 5 and 3 through 5 of the HCO+ vibrational states (03(1)0) and (03(3)0), respectively. Extrapolation of autoionizing series locates the positions of these rovibrational states to within +/-0,01 cm(-1 ). The use of this information combined with precise ionization limits fur lower vibrational states determined from earlier Rydberg extrapolations and spectroscopic information available from infrared absorption measurements enables an estimate of the force-field parameters for HCO+ bending. These p arameters include the harmonic bending frequency, omega(2) = 842.57 cm(-1), the vibrational angular momentum splitting constant, g(22) = 3.26 cm(-1), and the diagonal bending anharmonicity, x(22) = -2.53 cm(-1), separated fro m the off-diagonal contribution, x(12), by reference to ab initio calculati ons. Results of experiment on the higher vibrationally excited states of HC O+ are compared with recent theoretical predictions. (C) 2000 Academic Pres s.