A comparative spectroscopic study of the excited electronic states of potassium-neon and potassium-helium systems

Abstract

Configuration interaction studies have revealed the unexplored excited – state properties of potassium-neon and potassium-helium systems. In contrast to KHe, no potential barrier has been found in the lowest excited spin-orbit (1²Π_1/2) state of KNe. However, a small barrier of height 2 cm^-1 and width 1.9 Åhave been predicted for the 1²Π _u,1/2state of the triatomic Ne-K-Ne system. Both spin-orbit components (1²Π_{1/2, 3/2}) of the diatomic and triatomic systems of potassium-neon are characterized by low binding energy values. Radiative lifetimes of these states are almost 10 ns lower than that of potassium-helium systems. Their high-lying excited states are having better binding energy values, especially, that of the triatomic ones, while huge barriers are only noticed in the high-energy ²Σ⁺ states. Stable exciplexes can be expected to form with respect to the two energetically similar excited states of ²Δ and ²Π symmetries. They are having radiative lifetimes of 25 ns and involved in important transitions to the 1²Π state. This may eventually lead to the1²Π -X²Σ⁺ emission near 13 330 cm^-1 for KNe (12 900 cm^-1 for Ne-K-Ne), which is on the lower wavelength side in comparison to potassium-helium systems. Their low-lying repulsive excited states can trigger the pumping of the blue-side and the red-side of the n s ²S_1/2 → n p ²P_3/2 transition, and this may ultimately give rise to the n p ²P_1/2 → n s ²S_1/2 lasing transition.