Vacuum ultraviolet laser spectroscopy. IV. Spectra of Kr2 and constants of the ground and excited states

Abstract

Krypton dimers formed by supersonic jet expansion have been excited with tunable, and monochromatic VUV radiation leading to isotopically resolved fluorescence excitation spectra of three band systems at 125, 124, and 117 nm. Unambiguous upper‐state vibrational numbering was possible, resulting in evaluation of the spectroscopic constants for the three lowest excited states. From system I at ∼125 nm, with bands v’=32 to 38 and v‘=0, constants for the A ³Σ⁺_u state of Kr₂ were found to be T^’_e =74 303.9(8.0), ω_e =244.60(43), ω_ex^’_e =2.6045(60), and D_e=5807.0(8.0) cm⁻¹. Band system II at ∼124 nm, with bands v’=30 to 38 and v‘=0, led to constants for the B ¹Σ⁺_u state, T^’_e =75 426.8(1.7), ω_e =219.50(10), ω_ex^’_e =2.2325(15), and D_e =5629.1(2.5) cm⁻¹. Improved values for constants of the C ¹Σ⁺_u state were obtained from analysis of band system III at ∼117 nm (with bands v’=0 to 5, and v‘=0 to 2): T^’_e =85 520.60(10), ω_e =43.82 (10), ω_ex^’_e =1.812(18), and D_e =465.3(2.0) cm⁻¹. Vibrational constants for the ground state were obtained from bands with v‘=0, 1, 2, namely ω^‘_e =23.53(2) cm⁻¹ and ω_ex‘_e =1.07(1) cm⁻¹. Analyses of resolved rovibronic structure for all three band systems yielded values of rotational constants for the ground and three excited states, with the equilibrium internuclear distance r^‘_e =4.017(12) Å for ⁸⁴Kr₂. These new data were used to derive potential energy curves.