Spectroscopy of K2 Using Laser-Induced Fluorescence

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Abstract
When potassium vapor contained in a cell of aluminosilicate glass at 300°C is irradiated with the 6328‐Å line of the He–Ne laser, several fluorescence series are excited which originate from the B 1Πu state of the 39K2 molecule. Analysis of the fluorescence allows the spectroscopic constants (cm−1) of the X 1Σg+ ground state as measured by Loomis and Nusbaum to be corrected, giving ωe = 92.021, Be = 0.056743, ωexe = 2.829 × 10−1, αe = 1.65 × 10−4, ωeye = −2.055 × 10−3, γe = − 7.2 × 10−6, De = 8.63 × 10−8, δe = +1.5 × 10−7. The laser line is found to coincide with several molecular transitions. Three of these were determined from analysis of the spectrum to be (v″ = 0, J″ = 82) → (v′ = 7, J′ = 81), (v″ = 0, J″ = 18) → (v′ = 6, J′ = 17) , and (v″ = 1, J″ = 72) → (v′ = 8, J′ = 72) . Radiation from K atoms accompanying K2 excitation is also observed. It is proposed that the mechanism primarily responsible for the atomic potassium emission is the excitation transfer reaction K2*+K → K2 + K*, leaving the K2 molecule vibrationally excited.