CW all-optical triple-resonance spectroscopy of K₂: Deperturbation analysis of the A¹Σ_u⁺ (v ≤ 12) and b³Π_u (13 ≤ v ≤ 24) states

The lowest vibrational levels v = 0 to 12 of the A¹Σ_u⁺ state of K₂, which are perturbed by the b³Π_u state (13 ≤ v ≤ 24), were reexamined using all-optical triple-resonance (AOTR) spectroscopy. The experimental data were fitted by a nonlinear least-squares fit program to obtain deperturbed molecular constants for both the A¹Σ_u⁺ and b³Π_u states. Improved Dunham coefficients of the A¹Σ_u⁺ state in the range 0 ≤ v ≤ 62 are determined from the deperturbed T_v and B_v values including the v ≤ 12 region of this work, the v = 12-18 region in the work of Ross et al. [J. Phys. B.20, 6225-6231 (1987)], and the v = 21-62 region in the work of Lyyra et al. [J. Chem. Phys.92, 43-50 (1990)]. The electronic matrix element for the A¹Σ_u⁺ ∼ b³Π_u interaction is H_el = 18.64(9) cm^-1, in good agreement with the value of 18.4 (2) cm^-1 found by Ross et al.