New bands of the MgO A~1Π-X~1Σ~+ and a~3Π_(0,1)-X~1Σ~+ systems by Faraday laser magnetic resonance spectroscopy

摘要

Extended measurements are reported for rovibronic transitions between the strongly mixed low-lying X~1Σ~+, a~3Π and A~1Π electronic states of the MgO molecule in the 1640-3510 cm~(-1) region. The measurements were made with the Faraday laser magnetic resonance (LMR) technique utilizing a CO laser and a CO overtone laser. The new observed lines include the A~1Π-X~1Σ~+ (0-0, 0-1, 1-1, 1-2, 1-3, 2-2, 2-4, 3-3) bands as well as the much weaker a~3Π_(0,1)-X~1Σ~+ (0-0, 1-0) intercombination bands. The present highly precise LMR data provide a basis for performing an extensive deperturbation analysis including the spin-orbit, orbit-rotation and Zeeman interactions between the rovibronic levels of the X~1Σ~+, a~3Π and a~1Π states. Thereby the present data are combined with reliable earlier experimental results, in particular for the transitions involving higher lying vibronic states, in order to obtain the effective deperturbed molecular constants and perturbation parameters for the three lowest lying electronic states of MgO to as high an accuracy as possible. The absolute standard deviation of the LMR data is 6 x 10~(-4) cm~(-1) (18 MHz), which is in accord with the accuracy of our measurements. The set of deperturbed molecular parameters reproduces all measured lines with an overall standard deviation of 0.87 relative to the experimental uncertainties. For perturbations such as spin-orbit interaction there is good agreement with the predictions of large scale ab initio calculations.