LAMBDA-DOUBLING IN THE LAMBDA=2]-OVERTONE BAND IN THE INFRARED-SPECTRUM OF NO1

Λ-doubling in the first overtone, v = 2 ← 0, vibration-rotation band of 14N16O has been measured with Doppler-limited resolution using a tunable difference-frequency laser spectrometer. P- and R-branch Λ-splittings for 1 2 <- J ≤ 53 2 in the 2Π 1 2 electronic state and for 47 2 ≤ J ≤ 57 2 in the 2Π 1 2 state have been determined by least squares fitting of the spectral profiles to Gaussian doublets with a precision of better than ±1.5 MHz for the stronger, well-resolved lines. The Λ-doubling parameters obtained from a least square Hamiltonian analysis of the data for the v = 2 level are p2 = 349.542 (60) MHz and q2 = 2.754 (5) MHz with the error limits representing three standard deviations. These precise v = 2 parameters are combined with excellent v = 1 constants available in the literature to calculate the Λ-splittings expected in the v = 2 ← 1 hot band of NO for comparison with recently reported measurements. The effect of nuclear hyperfine structure on the lineshapes of some of the low J overtone transitions has also been observed. © 1979.