Cs(7DJ)＋H2的反应与非反应碰撞转移截面的测定

Experimental evaluation of reactive and nonreactive cross sections in Cs(7D)+H_2 collisions

利用激光泵浦-吸收技术,研究了在样品池中的Cs(7D_J)+H_2→CsH[X^1∑+(v″=0)]+H光化学反应过程。双光子激发Cs-H_2混合蒸气中Cs原子至7~2D态,荧光中除有泵浦能级发生的直接荧光外,还包含由精细结构碰撞转移产生的敏化荧光,CsH分子是由7D原子与H_2间的三体碰撞反应产生的。利用780 nm激光测量了CsH X^1∑+(v″=0→v″=21)吸收带。△Ⅰ′和△Ⅰ″分别表示泵浦7D_(3/2)和7D_(5/2)时的吸收光强。解速率方程组,得到7D_(3/2)→7D_(5/2)和7D_(5/2)→7D_(3/2)精细结构转移截面分别为(1.3±0.3)×10^(-14)和(9.8±2.0)×10^(-15)cm^2。从7D_J碰撞到7D以外态的截面分别为(4.0±1.0)×10^(-15)(对J=3/2)和(3.6+0.9)×10^(-15)cm^2(对J=5/2)。Cs(7D_J)+H_2→CsH+H的反应截面分别是(1.4±0.5)×10^(-16)(J=3/2)和(1.1±0.4)×10^(-16)cm^2(J=5/2),7D_(3/2)与H_2的反应活动性大于7D_(5/2)。

The Cs（7DJ）＋H2→CsH[X^1Σ^＋（v″=0）]＋H photochemical reaction was studied in a cell experimen.t by laser pump-absorption technique. Using two-photon exitation of the Cs7^2D atomic level in a Cs-H2 vapor mixture, the resulting fluorescence includes a direct component arising from the optically excited state and a sensitized component due to the collisionally populated fine-structure state. The CsH molecules are formed in three-body reactive collisions between exited Cs7^2D atoms and ground state H2 molecules. Nearinfrared absorption band CsH X^1Σ^＋（v″=21） near 780 nm was measured. The cross sections for the 7D3/2 →7D5/2 and 7D5/2 →7D3/2 fine-structure mixing are （1.3±0.3）× 10^-14 and （9.8±2.0）× 10^-15cm^2, respectively. The cross sections for collisional transfer from 7Dj to states other than 7D for J being 3/2 and 5/2 axe （4.0±1.0）× 10^-15 and （3.6±0.9）× 10^-15cm^2, respectively. The reaction cross sections [i.e.,Cs（7DJ）＋H2 -＋CsH＋H] for g being 3/2 and 5/2 are （1.4±0.5）× 10^-16 and （1.1±0.4）× 10^-16cm^2, respectively. The relative reactivity with H2 for two studied atoms is in an order of Cs（TD3/2） 〉Cs（7D5/2）.