Excitation Transfer between High-Lying States in K2 in Collisions with Ground State K and H2 Molecules
SHEN Xiao-yan1，LIU Jing2，DAI Kang2，SHEN Yi-fan2*
1. School of Chemistry and Molecular Engineering, East China University of Science & Technology, Shanghai 200237, China 2. School of Physics Science and Technique, Xinjiang University, Urumqi 830046, China
Abstract：Pure potassium vapor or K-H2 mixture was irradiated in a glass fluorescence cell with pulses of 710 nm radiation from an OPO laser, populating K2(1Λg) state by two-photon absorption. Cross sections for 1Λg-3Λg transfer in K2 were determined using methods of molecular fluorescence. During the experiments with pure K vapor, the cell temperature was varied between 553 and 603 K. The K number density was determined spectroscopically by the white-light absorption measurement in the blue wing of the self-broadened resonance D2 line. The resulting fluorescence included a direct component emitted in the decay of the optically excitation and a sensitized component arising from the collisionally populated state. The decay signal of time-resolved fluorescence from 1Λg→1 1Σ+u transition was monitored. It was seen that just after the laser pulse the fluorescence of the photoexcited level decreased exponentially. The effective lifetimes of the 1Λg state can be resolved. The plot of reciprocal of effective lifetimes of the 1Λg state against K densities yielded the slope that indicated the total cross section for deactivation and the intercept that provided the radiative lifetime of the state. The radiative lifetime (20±2) ns was obtained. The cross section for deactivation of the K2(1Λg) molecules by collisions with K is (2.5±0.3)×10-14 cm2. The time-resolved intensities of the K23Λg→1 3Σ+u(484 nm) line were measured. The radiative lifetime (16.0±3.2) ns and the total cross section (2.5±0.6)×10-14 cm2 for deactivation of the K2(3Λg) state can also be determined through the analogous procedure. The time-integrated intensities of 1Λg→1 1Σ+u and 3Λg→1 3Σ+u transitions were measured. The cross section (1.1±0.3)×10-14 cm2 was obtained for K2(1Λg)+K→K2(3Λg)+K collisions. During the experiments with K-H2 mixture, the cell temperature was kept constant at 553 K. The H2 pressure was varied between 40 and 400 Pa. The effects of K2-K collisions could not be neglected. These effects were subtracted out using the results of the pure K experiments. The cross section (2.7±1.1)×10-15 cm2 was obtained for K2(1Λg)+H2→K2(3Λg)+H2 collisions. The cross section is (6.8±2.7)×10-15 cm2 for K2(3Λg)+H2→ states out of K2(3Λg)+H2 collisions.
沈晓燕1，刘 静2，戴 康2，沈异凡2* . 高位K2分子与基态K原子及H2分子间的激发转移[J]. 光谱学与光谱分析, 2010, 30(02): 289-292.
SHEN Xiao-yan1，LIU Jing2，DAI Kang2，SHEN Yi-fan2* . Excitation Transfer between High-Lying States in K2 in Collisions with Ground State K and H2 Molecules . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2010, 30(02): 289-292.
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