Laser spectroscopic studies of the E1Σ+ `Rydberg' state of the MgO molecule

Abstract

The E 1 Σ + state of 24 Mg 16 O has been characterized by two-color Resonance-Enhanced Two-Photon Ionization (R2PI) spectroscopy in the 36,000-40,000 cm-1 region. Several rotationally resolved bands, assigned consistently to 24 Mg 16 O(E 1 Σ + ← X 1 Σ +) vibronic transitions, have been analyzed. The effective B v′ (v′ = 0-8) constants determined exhibit an unusual variation with v′. Possible causes of this variation are discussed. The vibrational level spacings in the E 1 Σ + state (v′ = 0-7) also provide evidence for a weak homogeneous (Ω = 0 +) perturbation. Estimated spectroscopic constants for the E 1 Σ + state are reported.

Characterisation of the ground X+ 2ΠΩ and first excited A+ 2Σ+ electronic states of MgO+ by high-resolution photoelectron spectroscopy

“…In this region, one primarily observes transitions from the X 1 Σ + electronic ground state to the E 1 Σ + , F 1 Π, and G 1 Π electronic states previously assigned and characterised by Bellert et al 26,27 and Wang et al 28 In the case of the G 1 Π state, no vibrational assignment could be derived so far, and we have adopted the labels “ A ”, “ B ”, “ C ”, “ D ”, etc. introduced by Bellert et al 26,27 and Wang et al 28 to designate the observed vibrational levels in the order of increasing wavenumber. Surprisingly, vibrational levels up to v ′′ = 6 in the ground X 1 Σ + state are significantly populated in the supersonic beam, indicating that hardly any cooling of the vibrational degree of freedom takes place in the supersonic expansion.…”

“…4 shows a survey R2PI spectrum from 37 500 to 39 000 cm −1 , with the vibronic transitions labelled as . In this region, one primarily observes transitions from the X 1 Σ + electronic ground state to the E 1 Σ + , F 1 Π, and G 1 Π electronic states previously assigned and characterised by Bellert et al 26,27 and Wang et al 28 In the case of the G 1 Π state, no vibrational assignment could be derived so far, and we have adopted the labels “ A ”, “ B ”, “ C ”, “ D ”, etc. introduced by Bellert et al 26,27 and Wang et al 28 to designate the observed vibrational levels in the order of increasing wavenumber.…”

“…The assignments of the E 1 S + -X 1 S + , F 1 P-X 1 S + , and G 1 P-X 1 S + transitions are based on previous work by Breckenridge and coworkers. [26][27][28] The progressions marked in green and orange colours are assigned in Table 1. Unassigned bands are marked with asterisks.…”

“…Strong configurational mixing also affects the valence electronically excited states of MgO, 1,2,15,16,20,21 which have been studied experimentally by laser 18,[22][23][24] and microwave 24,25 spectroscopy. Particularly noteworthy are the detailed investigations of the F 1 P, E 1 S + and G 1 P electronic states [26][27][28][29] and the 3 P 2 states 30 at term values in the range of 36 000-40 000 cm À1 above the ground state. Breckenridge and coworkers have used these excited states to determine the adiabatic ionisation energy of MgO (64 578(7) cm À1 ) by resonance-enhanced twophoton ionisation (R2PI) spectroscopy.…”

A multidisciplinary study on magnesium

“…Newer experimental studies, including optical spectroscopy, laser-magnet resonance, laser-induced fluorescence, two-colour resonance-enhanced two-photon ionization studies and vibrationally resolved photoelectron spectroscopy [25][26][27][28][29][30][31][32][33][34][35][36][37] have been cited in a recent theoretical study by Maatouk et al 38 Comparing the data collected by HH and PG, it could be stated that HH included in their book the A 2 Σ + -X 2 Σ systems in the (infra-red) region at about 1900 nm, which was only indirectly mentioned by PG. The reason might be that the first reference used by HH 39 appeared between the third and fourth editions of PG's book, and the second one 40 even later.…”