林金全臺灣大學：化學研究所張雅嵐Chang, Ya-LanYa-LanChang2007-11-262018-07-102007-11-262018-07-102004http://ntur.lib.ntu.edu.tw//handle/246246/51851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。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.Chapter 1 : Introduction……………………..………………….....1 A. Reaction dynamics of electronically excited alkali atom and hydrogen molecule………………………………………….…..2 B. Reaction dynamics of electronically excited alkaline earth atoms with RH(R=H, CH3, and SiH3) molecules…………………..…..9 C. Methods to study the reaction mechanism……………………...14 D. Reactions of Ca(4 1P1) and Mg(3 1P1) with H2…………………16 E. References………………………………………………...…….19 Chapter 2 : Principles……………………….……………………22 A. Spectra of diatomic molecules……………………………….…23 A-1. Rotation……………………………...……………………23 (1) Rigid rotator……………………………………………..23 (2) Nonrigid rotator…………………………………………25 A-2. Vibration……………………………………….…...……..26 (1) The Harmonic Oscillator………………………………...26 (2) The Anharmonic Oscillator…………………...…………27 A-3. Selection rule for transition………………...……………..28 A-4. Franck Condon Factor………………………...…………..29 A-5. Hönl-London Factor……………...……………………….30 A-6. Thermal distribution of quantum states; Intensities in rotation- vibration spectra………………………………..30 A-7. Laser-induced fluorescence (LIF)………...………………31 B. ab-initio methods……………………………………………….33 B-1. Hartree-Fock method……………………………………...33 B-2. SCF techniques……………………………………………35 C. Reference…………………………………………………….….36 Chapter 3 : Experiment…………………………………………..37 A. Instruments……………………………………………………..38 A-1. Heat pipe apparatus………………………………...……..38 A-2. Laser system………………………………………………40 (1) Nd:YAG Laser……………………………………...…...40 (2) Dye laser...........................................................................41 A-3. Digital Oscilloscope………………………………………41 A-4. Control systems………………………………………...…42 (1) Time : Delay generator (DG535)………………….…......42 (2) Temperature : Thermal couple…………………………...43 (3) Pressure : MKS pressure gauge… ………………….…...44 A-5. Data acquisition program…………………………….…...44 (1) BOXCAR integrator……………………………….........44 (2) Interface card : SR245…………………………………..44 A-6. Detection systems…………………………………………45 (1) PMT…………………………………………………......45 (2) Photodiode………………………………………………46 (3) Band pass filter………………………………………….46 B. Dye……………………………………………………………...47 B-1. LDS925……………………………………………….…47 B-2. DCM…………………………………………………….47 C. Summary of experimental steps…………………………..…….48 Chapter 4 : Results……………………………………………...…51 A. Laser induced fluorescence spectrum……………………..……52 B. Dependence………………………………………………..……54 B-1. Pressure dependence……………………………..………54 B-2. Delay time dependence…………………………………..55 B-3. Temperature dependence…………………………………56 C. Data processing…………………………………………….…….60 C-1. Assignment…………………………………...…………..60 C-2.Normalization…………………………………………..…63 (1) Laser intensity variation with wavelength…………...….63 (2) Band pass filter transmittance……………………...……64 C-3. Rotational distribution……………………………………65 C-4. Rotational temperature……………………………...……66 C-5. Energy disposal…………………………………………...67 (1) available energy…………………………………………67 (2) rotational energy………………………………….……..68 (3) vibrational energy…………………………………….…69 (4) translational energy…………………………………..….69 D. Data shown in Tables……………………………………..……...70 E. References……………………………………………………..…70 Chapter 5 : Discussion…………………………..….……………71 A. Understanding reaction pathway with aid of PES calculations….72 A-1. Ca(31D) approaches H2 in C∞v symmetry……………....…72 A-2. Ca(31D) approaches H2 in C2v symmetry………………....73 B. Comparison between Ca(31D) and Ca(41P1) reactions with H2…74 B-1. different potential energy surface characteristics………….74 B-2. reaction coefficient………………………………………...75 B-3. reasons for higher rotational energy fraction than Ca(41P1).77 (1) large torque ………………………………………………77 (2) short-lived intermediate…………………………………..77 B-4. insignificant contribution from the Ca(41P1)………………78 B-5. The CaH(v=0,1) populations………………………………79 C. References………………………………………………..……..80 Chapter 6 : Conclusions………………………………………….811289852 bytesapplication/pdfen-US激發偵測反應動力學氫氣鈣雷射誘導螢光LIFpump probedynamicH2Cathesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/51851/1/ntu-93-R91223030-1.pdf