Theoretical study of pressure broadening of lithium resonance lines by helium atoms

Abstract

Quantum mechanical calculations are performed of the emission and absorption profiles of the lithium 2s-2p resonance line under the influence of a helium perturbing gas. We use carefully constructed potential energy surfaces and transition dipole moments to compute the emission and absorption coefficients at temperatures from 200 to 3000 K at wavelengths between 500 nm and 1000 nm. Contributions from quasi-bound states are included. The resulting red and blue wing profiles are compared with previous theoretical calculations and with an experiment, carried out at a temperature of 670 K.

Theoretical study of sodium and potassium resonance lines pressure broadened by helium atoms

“…The spectra for NaHe and KHe are similar in shape to each other and to LiHe [9] but shifted in wavelength. At low temperatures there occur broad maxima in the emission coefficients at around 670 nm for NaHe and 830 nm for KHe, compared to 870 nm for LiHe.…”

“…Thus we consider both bound-free and free-free transitions. The details of the quantum mechanical calculation of pressure broadening are given in our previous paper [9].…”

“…In a recent paper [9], we studied the pressure broadening of the lithium 2s-2p resonance line. Here we consider the broadening of the 3s-3p line of sodium and the 4s-4p line of potassium arising from collisions with helium atoms.…”

K–H2line shapes for the spectra of cool brown dwarfs

“…The blue satellites in the far wing of alkali-He/H 2 line profiles are correlated with the maxima in the difference potentials ∆V for the B-X transition (Allard et al 2003(Allard et al , 2005(Allard et al , 2007cAllard & Spiegelman 2006;Zhu et al 2005Zhu et al , 2006. Details on the properties of the K-H 2 quasi-molecular line satellite have been reported in Allard et al (2003Allard et al ( , 2007c.…”

Theoretical and laboratory spectra of sodium perturbed by molecular hydrogen

“…These satellite bands of alkali metals perturbed by rare gas have been extensively studied in the past (Allard & Kielkopf 1982, and references therein). There was a renewal of interest (Burrows & Volobuyev 2003;Allard et al 2003Allard et al , 2005Allard et al , 2007cAllard & Spiegelman 2006;Zhu et al 2005Zhu et al , 2006Alioua & Bouledroua 2006;Alioua et al 2008) because alkali-metals are a prominent source of opacity in the spectra of brown dwarfs (Allard et al 2003(Allard et al , 2007a. Blue satellite bands in alkali-He/H 2 profiles can be predicted from the extrema in the difference potentials ΔV(R), given by…”