Precision frequency measurement of N_2O transitions near 4.5 μm and above 150 μm

摘要

Frequency measurements are given for the 10~00←00~00 band of N_2O near 4.5 μm and for pure rotational transitions beyond 151.5 μm. The infrared measurements utilize a periodically poled lithium niobate (PPLN) based difference frequency generation (DFG) source locked to the saturated absorption center of an N_2O absorption line. The DFG frequency is calibrated by an optical frequency comb and an iodine hyperfine transition. We report 44 transitions ranging from J = 1 - 100 for both the P and R branches and the accuracy is better than 10 kHz for most transitions. In addition, 175 pure rotational transitions have been measured including 33 measurements with sub-Doppler precision (≤3 kHz), and 142 Doppler limited measurements. These are combined with other precision rotational and vibrational measurements to provide improved quantum mechanical parameters, as well as frequency calibration tables for the N_2O bands near 4.5 μm.