Wang Min, Zhou Dong-Dong, Wang Xue-Yan, Mu Nisai Nu, Dai Kang, Wang Qian, Shen Yi-Fan
College of Physics Science and Engineering, Xinjiang University, Urumqi 830046, China.
Guang Pu Xue Yu Guang Pu Fen Xi. 2009 Nov;29(11):2889-92.
With a Cs density of -10(15) cm(-3) and typically -2% Cs2, cesium vapor was irradiated in a glass fluorescence cell with pulses of radiation from a YAG-laser- pumped OPO laser, populating Cs2 (B 1IIu) state by one-photon absorption. Predissociation of the B 1IIu state and energy transfer in Cs2 (B 1IIu)+Cs(6S) collisions were studied using methods of atomic and molecular fluorescence. The B 1IIu (v < 10) state does not predissociate in Cs vapor excited at lambda = 736 nm. The decay signal of the time-resolved fluorescence from the B 1IIu --> X 1sigma(g)+ transition was monitored. According to the Stern-Volmer equation, a plot of reciprocal of effective lifetimes of the Cs2 (B 1IIu) state quenched by Cs(6S) atoms against its densities yielded a slope that indicated the total cross section for deactivation and an intercept(at which the Cs pressure is zero) that provided the information on the radiative lifetime of the state. The radiative lifetime is (35 +/- 7)ns for the B 1IIu state. The total cross section for deactivation of excited Cs2 [B 1IIu (v < 10)] molecules by means of collisions with Cs atoms is (4.0 +/- 0.5) x 10(-14) cm2. The B 1IIu (v > 30) state pre-dissociates in Cs vapor excited at lambda = 705 nm. At the different Cs densities, the relative time-integrated intensities of the resulting Cs emission lines, I(6P1/2 --> 6S1/2) [I(D1)] and I(6P3/2 --> 6S1/2) [I(D2)], and Cs2 (B 1IIu) band-pass (725 --> 735 nm) I[Cs2 (B 1IIu)] were measured. By combining Cs 6P fine-structure mixing and quenching induced by collisions with ground Cs atoms, the authors obtained absolute values for predissociation and collisional transfer cross sections. The predissociation rates are (4.3 +/- 1.7) x 10(6) s(-1) (for predissociating to 6P3/2) and (4.7 +/- 1.9) x 10(6) s(-1) (for predissociating to 6P1/2), respectively. The collisional transfer cross sections are (0.45 +/- 0.18) x 10(-14) cm2 (for transfering to 6P1/2) and (4.3 +/- 1.7) x 10(-14) cm2 (for transfering to 6P3/2). These experimental results show that if Cs2 excited state is predissociation state, it can produce Cs(6P) atoms by predissociation and collisional transfer; if Cs2 excited state is bound, it can produce produce Cs(6P) atoms by collisional transfer.
铯蒸汽的密度为-10(15) cm(-3)，通常含有-2%的Cs2，在玻璃荧光池中用YAG激光泵浦的OPO激光脉冲对其进行辐照，通过单光子吸收使Cs2 (B 1IIu)态布居。利用原子和分子荧光方法研究了B 1IIu态的预解离以及Cs2 (B 1IIu)+Cs(6S)碰撞中的能量转移。在λ = 736 nm激发的铯蒸汽中，B 1IIu (v < 10)态不会预解离。监测了B 1IIu --> X 1sigma(g)+跃迁的时间分辨荧光的衰减信号。根据斯特恩-沃尔默方程，将被Cs(6S)原子猝灭的Cs2 (B 1IIu)态的有效寿命的倒数对其密度作图，得到的斜率表示失活的总截面，截距（此时铯压力为零）提供了该态辐射寿命的信息。B 1IIu态的辐射寿命为(35 +/- 7)ns。通过与Cs原子碰撞使激发的Cs2 [B 1IIu (v < 10)]分子失活的总截面为(4.0 +/- 0.5) x 10(-14) cm2。在λ = 705 nm激发的铯蒸汽中，B 1IIu (v > 30)态会预解离。在不同的Cs密度下，测量了产生的Cs发射线I(6P1/2 --> 6S1/2) [I(D1)]和I(6P3/2 --> 6S1/2) [I(D2)]以及Cs2 (B 1IIu)带通（725 --> 735 nm）I[Cs2 (B 1IIu)]的相对时间积分强度。通过结合Cs 6P精细结构混合和与基态Cs原子碰撞引起的猝灭，作者获得了预解离和碰撞转移截面的绝对值。预解离速率分别为(4.3 +/- 1.7) x 10(6) s(-1)（预解离到6P3/2）和(4.7 +/- 1.9) x 10(6) s(-1)（预解离到6P1/2）。碰撞转移截面分别为(0.45 +/- 0.18) x 10(-14) cm2（转移到6P1/2）和(4.3 +/- 1.7) x 10(-14) cm2（转移到6P3/2）。这些实验结果表明，如果Cs2激发态是预解离态，它可以通过预解离和碰撞转移产生Cs(6P)原子；如果Cs2激发态是束缚态，它可以通过碰撞转移产生Cs(6P)原子。
