The ν_{7} vibrational states of C _{3}O _{2}. A leastsquares fit of the rigidbender model to the v_{7}ν_{7}^{l7} energies and rotational constants
Abstract
The rigidbender model is used to treat the largeamplitude, lowfrequency, bending vibration ν_{7} of C _{3}O _{2}. Different parameterizations of the bending potential function are considered, and a simple twoterm power series is found to give the best fit. With this parameterization, using a leastsquares fit to energies and B values, the ν_{7} potential function is determined for the ground state as well as for the states in which ν_{2}, ν_{3}, ν_{4}, ν_{6}, 2 ν_{6}, ν_{1} + ν_{3}, ν_{1} + ν_{4}, ν_{2} + ν_{3}, and 2 ν_{2} + ν_{4} are excited. The excitation of other vibrations has in some cases a drastic effect on the ν_{7} potential. In the ground state the potential has a 29 cm ^{1} barrier at the linear position, in ν_{1} + ν_{3} the barrier increases to 79 cm ^{1}, while in 2 ν_{2} + ν_{4} the barrier vanishes. An equilibrium potential is determined by correcting the ground state potential for the effects of zeropoint motion of the normal vibrations ν_{1}, …, ν_{6}. This potential has a 35.6cm ^{1} barrier with a minimum at α = 11.14°, where 2α is the angular deviation from linearity. The model accurately predicts the quartic and sextic centrifugal distortion terms for the lowlying v_{7}ν_{7}^{l7} states. Secondorder ltype coupling is included in the calculations of the quartic terms. The effects of this coupling, which are most pronounced for the ν_{7} ≥ 2 states, adequately explain the negative D term recently reported for the ν_{2} + 4 ν_{7}^{0} state.
 Publication:

Journal of Molecular Spectroscopy
 Pub Date:
 February 1980
 DOI:
 10.1016/00222852(80)902210
 Bibcode:
 1980JMoSp..79..396W