Electric-field-induced Q branch of the vibrational fundamental of CO

Abstract

The electric-field-induced Q branch of the vibrational fundamental has been observed for the first time in a polar diatomic molecule in a study of 12C16O near 2143.−1 Intensity measurements of the Q(0), Q(1), and Q(2) transitions with a diode laser spectrometer have shown that these normally forbidden lines become allowed through the mixing of rotational levels generated by the interaction of the dipole moment with the externally applied electric field. Measurements have been made both with a static field and with a square-wave-modulated field. The electric dipole moment of 12C16O in the first-excited vibrational state, not previously measured experimentally, has been found to equal −0.0830 (23) D. The transition moment for the vibrational fundamental has been determined to be 0.1077 (38) D, which is in agreement with previous, more precise determinations based on the intensity of the allowed P and R branches. The results obtained here are in excellent agreement with earlier calculations of the dipole moment function.