Laser spectroscopy of the CaOH A 2Π–X 2Σ+ (020)–(000) band: Deperturbation of the Fermi resonance, Renner–Teller, and spin–orbit interactions

The A 2Π–X 2Σ+ (020)–(000) band of CaOH has been observed using cw dye laser excitation, and rotationally analyzed. The measured line positions, in combination with data obtained in our laboratory for the A 2Π–X 2Σ+ (100)–(000) band, have been employed in a global deperturbation of the A(100) 2Π and A(020)κ 2Π and μ 2Π vibronic states that simultaneously takes account of Fermi resonance, the Renner–Teller effect, and spin–orbit coupling. All the measured line positions are reproduced to within the measurement accuracy of 0.005 cm−1. The Renner–Teller and Fermi resonance parameters in the CaOH A 2Π state have been determined: εω2=−36.569 19(97) cm−1 and W1=10.300 58(54) cm−1.