Heterodyne frequency measurements on N_2O at 53 and 90 μm

Heterodyne frequency measurements on the 0111–0000 band of N2O have been made with the use of a tunable-diode laser, a CO laser transfer oscillator, and a CO2 laser frequency synthesizer. A beat frequency was measured between a CO laser and a tunable-diode laser whose frequency was locked to the peak of N2O absorption features. The frequency of the CO laser was simultaneously determined by measuring the beat frequency with respect to a reference synthesized from two CO2 lasers. New rovibrational constants are given for the 0111 state of N2O, which are in excellent agreement with previous results, although the band center is 4 MHz higher than in the previous measurements. A table of the line frequencies and their absolute uncertainties is given for the N2O absorption lines in the wave-number region from 1830 to 1920 cm−1. Some additional frequency measurements near the lower-frequency end of the 0200–0000 band have also been made with respect to a 12C18O2 laser.