Absorption spectrum of Kr2F(4 2Γ) in the near ultraviolet and visible (335≤λ≤600 nm): Comparison with Kr+2(1( 1/2 )u) measurements

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Abstract
Absolute photoabsorption cross sections for the lowest excited state (4 2Γ) of Kr2F and the ground state (1( 1/2 )u) of Kr+2 have been measured in the visible and ultraviolet (Kr2F: 248, 308, 335–600 nm; Kr+2 : 360–500 nm). As predicted by theory, the Kr2F spectrum is dominated by the 9 2Γ←4 2Γ band which peaks below 340 nm and correlates with the Kr+2 2( 1/2 )g ←1( 1/2 )u transition. However, Kr2F(4 2Γ) and Kr+2 (1( 1/2 )u) both absorb more strongly for wavelengths beyond ∼450 nm than expected, apparently owing to a nonthermalized Kr+2 vibrational distribution. Despite interference from Kr2F stimulated emission between ∼350 and 460 nm, the experimental results show the Kr2F(4 2Γ) and Kr+2 absorption profiles to be similar for λ≥460 nm but diverging rapidly as λ increases from 335 to 360 nm. At 360 nm, the absorption cross sections differ by a factor of 3. Contrary to theoretical expectations, the Kr2F absolute absorption cross section is consistently smaller (typically +2 which suggests that the impact of F− on the Kr+2 oscillator strengths is significant.