Rydberg spectroscopy of calcium monofluoride

Abstract

Considered to be a prototype for e⁻ <--> nuclear interaction in more complex molecules, the Alkaline earth monohalides (MX) have a simple electronic structure which consists of two closed-shell atomic ions (M²⁺ + X) in the ion-core and a non-bonding electron in the outer orbital. Their Rydberg spectra will reveal the Rydberg e⁻ <--> ion-core interaction in the simplest case. This thesis presents the experimental results of Calcium Monofluoride (CaF) in the n* = 17 to 18, v⁺ = 1 autoionizing region, of which the OODR (Optical-Optical Double Resonance) spectra were recorded from its D² [sigma]⁺ intermediate state. Since the predissociation limit of CaF lies only 2,800 cm⁻¹ (n* [approximately] 6.3) below its first ionization potential, it had long been believed that the predissociation of CaF has little effect on the spectra. It is surprising that our observations show that in fact the predissociation of CaF can be important and change the appearance of the spectra in the autoionizing region. In the spectra from the low energy region, the line patterns of core-penetrating states are strong and they repeat in consecutive n*-supercomplexes; however, in the n* = 17 to 18, v⁺ = 1 autoionizing region, the core-penetrating states start to disappear due to predissociation and the non-penetrating states become the dominant spectroscopic feature.