激發態鈣原子(3D)與氫氣分子之反應動力學研究

The dynamic study of the excited Ca atom (3D) reaction with H2 molecule

張雅嵐(Ya-Lan Chang)

指導教授 ： 林金全

國立臺灣大學/理學院/化學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.01581

摘要

經由激發-偵測技術，可以得到 Ca(4s3d 1D)+H2 →CaH(X2Σ+)+H 反應的初生態產物CaH的轉動振動分佈圖譜。藉由分析轉動振動圖譜，可以進一度推測得知反應機制主要是採插入式。而初生態CaH在不同振動態v=0以及1的分佈比率是 CaH(v=0)/CaH(v=1) = 3.3±0.5，對應到的波茲曼振動溫度是1518±202 K，v=0及1的轉動分佈對應到的波茲曼分佈溫度分別是807±31 K與684±56 K。產物CaH的轉動以及振動能量分別是388±38 cm-1與292±29 cm-1。根據阿瑞尼士理論，利用溫度效應實驗得知，該反應路徑沒有面臨到能障，並搭配位能面理論計算可以推測該反應路徑偏向以近乎C2v立體位向，鈣原子插入氫氣鍵之間而發生反應產生產物CaH，而氫氣鍵長在其平衡鍵長0.75 Å時，即有機會發生反應。和Ca(41P1)與氫氣反應相比較，推測Ca(31D)與氫氣產生的CaH其中間產物生命期較短，而來不及將能量重新分配，以致於會有較高比率的能量(38%)分佈在產物的轉動。

關鍵字

激發偵測 ； 反應動力學 ； 氫氣 ； 鈣 ； 雷射誘導螢光

並列摘要

The nascent CaH product in the reaction Ca(4s3d 1D)+H2 → CaH(X2Σ+)+H is obtained using a pump-probe technique. The nascent CaH (v=0,1) distributions, with a population ratio of CaH(v=0)/CaH(v=1) = 3.3±0.5, may be characterized by Boltzmann rotational temperature of 807±31 and 684±56 K for the v=0 and 1 levels, respectively, and a Boltzmann vibrational temperature of 1518±202 K. The rotational and vibrational energy partitions in CaH have been estimated to be 388±38 and 292±29 cm-1, respectively. According to Arrhenius theory, the temperature dependence measurement shows no potential barrier for the current reaction. With the aid of the potential energy surfaces (PESs) calculations, the reaction pathway favors a Ca insertion into the H2 bond along a (near) C2v geometric approach. The reaction will occur when H-H is at its equilibrium bond distance, 0.75 Å. The high rotational energy distribution (38%) of the nascent CaH product may be reasonably interpreted from the nature of the short-lived intermediate structure comparing with those of Ca(41P1) reaction with H2.

並列關鍵字

LIF ； pump probe ； dynamic ； H2 ； Ca

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