High-accuracy transition frequencies for the O2A-band

Frequencies for 32 P-branch transitions of the O2A-band (b1Σg+←X3Σu-) were measured between 12 975 and 13 115 cm−1 using the frequency-stabilized cavity ring-down spectrometer located at National Institute of Standards and Technology, Gaithersburg, MD. Absolute line positions were calibrated using the hyperfine components of 39K D1 and D2 atomic transitions yielding uncertainties <1 MHz (∼3 × 10−5 cm−1). Spectroscopic parameters for the b1Σg+(v=0) state were calculated and compared with previously determined values. These new transition frequencies should serve as a convenient secondary calibration standard in the 760 nm region.