Mesospheric wind determinations and the P₁ (2)c,d lines of the X ²∏ OH (8‐3) band

Mesospheric winds have been determined from ground‐based optical measurements of the nighttime sky emission of the P 1 (2) lines of the X ²∏ OH (8 ‐ 3) band. The measured winds indicate a 12‐hour periodicity with amplitude near 30 m/s, and presumably associated with tidal motions. The frequencies (wavelengths) of these Λ‐doubled P 1 (2) c,d lines have been measured to be 13 664.44 4 K (731.6428 nm) and 13 664.31 0 K (731.6320 nm), with a standard deviation of the mean of 0.001 K (0.00007 nm). The spacing between the two P 1 (2) lines is found to be 0.134 6 ±0.00005 K. Incidental to this study is the determination of the frequency (wavelength) of a Xenon line in this region of the spectrum found at 13 663.27 4 K (731.6874 nm), with the same uncertainty level as the OH lines.