高位K_2分子与基态K原子及H_2分子间的激发转移

激光双光子激发K2至1Λg高位态,利用分子荧光光谱方法,研究了1Λg-3Λg间的碰撞转移截面。在纯K实验中,池温控制在553至603 K之间,K原子密度由光学吸收法测量得到。探测1Λg-11Σu+的直接时间分辨荧光的光强,它是一条纯指数衰减曲线,由此得到1Λg+态的有效寿命,有效寿命的倒数与K密度成线性关系,从直线的斜率得到1Λg态的猝灭截面为(2.5±0.3)×10-14cm2,从截距得到辐射寿命为(20±2)ns。由3Λg→13Σu+转移荧光的时间分辨谱,用类似的方法得到3Λg的猝灭截面为(2.5±0.6)×10-14cm2,辐射寿命为(16.0±3.2)ns。由1Λg→11Σu+与3Λg→13Σu+的时间积分强度比得到K2(1Λg)+K→K2(3Λg)+K的转移截面为(1.1±0.3)×10-14cm2。在K2-H2碰撞实验中,池温保持在553 K,K密度为5×1015cm-3,H2气压在40~400 Pa之间,其中K2-K碰撞效应是不能略去的,但可以用纯K结果扣除,得到K2(1Λg)+H2→K2(3Λg)+H2的碰撞转移截面为(2.7±1.1)×10-15cm2。K2(3Λg)+H2→K2(3Λg)以外态+H2的猝灭截面为(6.8±2.7)×10-15cm2。

Excitation Transfer between High-Lying States in K_2 in Collisions with Ground State K and H_2 Molecules

Pure potassium vapor or K-H_2 mixture was irradiated in a glass fluorescence cell with pulses of 710 nm radiation from an OPO laser,populating K_2(~1∧_g)state by two-photon absorption.Cross sections for ~1∧_g-~3∧_g transfer in K_2 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 D_2 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 ~1∧_g→1~1∑_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 ~1∧_g state can be resolved.The plot of reciprocal of effective lifetimes of the ~1∧_g 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 K_2(~1∧_g)molecules by collisions with K is(2.5±0.3)×10~(-14) cm~2.The time-resolved intensities of the K_2 ~3∧_g→1~3 ∑_u~+ (484 um)line were measured.The radiative lifetime(16.0±3.2)ns and the total cross section(2.5±0.6)×10~(-14) cm~2 for deactivation of the K_2(~3∧_g)state can also be determined through the analogous procedure.The time-integrated intensities of ~1∧_g→1 ~1∑_u~+ and ~3∧_g→∑_u~+ transitions were measured.The cross section(1.1±0.3)×10~(-14) cm~2 was obtained for K_2(~1∧_g)+K→K_2(~3∧_g)+K collisions.During the experiments with K-H_2 mixture,the cell temperature was kept constant at 553 K.The H_2 pressure was varied between 40 and 400 Pa.The effects of K_2-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) cm~2 was obtained for K_2(~1∧_g)+H_2→K_2(~3∧_g)+ H_2 collisions.The cross section is(6.8±2.7)×10~(-15) cm~2 for K_2(~3∧_g)+ H_2→states out of K_2(~3∧_g)+H_2 collisions.