Optical-optical double resonance with two dye lasers: Rotational analysis of the E²Σ-B²Σ system of Ca³⁵Cl

A complete rotational analysis of the E ²Σ-B ²Σ system of CaCl has been accomplished using two tunable dye lasers. The first cw laser is tuned to a known B ²Σ-X ²Σ transition to produce a finite concentration of molecules in a particular quantum state. Subsequently, a second pulsed dye laser is used to record the E ²Σ-B ²Σ excitation spectrum from this state prepared level. The method vastly simplifies an otherwise congested molecular spectrum. The data are combined with previous microwave measurements on the X ²Σ state and optical data on the B²Σ- X²Σ system to give the following molecular constants (cm ^-1). Uncertainties are 95% confidence limits in the last digit. X²Σ B²Σ E²Σ T_e 0 16 856.69(2) 34268.17(98) ω_e 369.8(10) 366.8(10) 413.7(16) ω_eX_e 1.13(20) 1.28(20) 1.67(82) B_e 0.1522325(45) 0.1546940(82) 0.163412(17) α_e 7.998(39) × 10^-4 8.839(67) × 10^-4 8.66(10)× 10 ^-4 γ_av(spin rotation) 0.00135(6) -0.0652(2) 0.0046(5)