本文選題：飛秒激光 + 六極桿靜電場��； 參考：《吉林大學(xué)》2016年博士論文

【摘要】：論文以鹵代甲烷分子為例,結(jié)合實驗與理論研究了分子在六極靜電場與飛秒激光場的共同作用下的準(zhǔn)直行為,討論了如何通過速度成像實驗數(shù)據(jù)中直接提取出分子準(zhǔn)直程度參數(shù)〈P_2(cosθ)〉二階勒讓德多項式的平均值)的實驗方法以及理論依據(jù),由此得到了清晰和系統(tǒng)的對于分子轉(zhuǎn)動動力學(xué)機(jī)制的認(rèn)識。利用制備的準(zhǔn)直與反準(zhǔn)直分子,通過離子電離產(chǎn)額測量與電子成像實驗,從不同側(cè)面深入研究了鹵代甲烷分子在強(qiáng)激光場中的電離行為。多原子分子在飛秒強(qiáng)激光場中的電離過程由于其量子態(tài)復(fù)雜性和多粒子關(guān)聯(lián)一直是強(qiáng)場物理領(lǐng)域中的研究熱點,尤其是在當(dāng)激光強(qiáng)度介于多光子電離區(qū)與隧穿電離區(qū)之間時,目前還有很多物理問題尚未得到明確的解釋。分子的準(zhǔn)直技術(shù)可以將實驗室坐標(biāo)系與分子坐標(biāo)系聯(lián)系起來,這使得在分子坐標(biāo)系下的強(qiáng)場物理研究成為了可能,同時也要求新實驗探測技術(shù)的發(fā)展。我們發(fā)展了一套靜電六極桿結(jié)合速度成像探測的實驗裝置,通過六極桿轉(zhuǎn)動態(tài)選擇,這一實驗技術(shù)利用靜電場與分子偶極矩之間的斯塔克效應(yīng)可以得到處于|1±1(?)〉轉(zhuǎn)動量子態(tài)的對稱陀螺鹵代甲烷分子。態(tài)選擇后的分子通過與一束800 nm、偏振方向垂直于飛行時間質(zhì)譜裝置中靜電提取場的線偏飛秒激光發(fā)生相互作用而被非絕熱準(zhǔn)直,隨后分子被可控制時間延遲的第二束飛秒同偏振方向的線偏激光探測。理論上我們模擬了處于|1±1(?)1〉轉(zhuǎn)動態(tài)的碘甲烷分子在準(zhǔn)直激光偏振矢量垂直于離子透鏡靜電場這種垂直幾何情況下的轉(zhuǎn)動波包結(jié)構(gòu)。在僅使用振幅尺度因子一個變量的情況下,實驗測量的離子信號的轉(zhuǎn)動波包周期形狀重現(xiàn)了理論模擬的結(jié)果。可以看出,在速度成像裝置慣常使用的垂直幾何條件下,當(dāng)準(zhǔn)直激光強(qiáng)度足夠強(qiáng)時產(chǎn)生離子對應(yīng)的牛頓球相比于純柱對稱性的偏差小到可以忽略。理論模擬得到的準(zhǔn)直參數(shù)在轉(zhuǎn)動波包周期中最大和最小值位置處都與速度成像實驗結(jié)果中提取出的準(zhǔn)直參數(shù)對應(yīng)的很好。實驗中這種激光誘導(dǎo)可控的準(zhǔn)直程度的上下極限可以達(dá)到〈P_2(cosθ)〉=0.7和〈P_2(cosθ)〉=-0.1。本文工作中完成了ppt理論程序的編寫與調(diào)試,通過與惰性氣體kr和xe在激光強(qiáng)度從1013w/cm2到1015w/cm2范圍內(nèi)電離產(chǎn)額實驗結(jié)果相比較,驗證了該ppt理論程序的可靠性并且實現(xiàn)了對于光強(qiáng)的標(biāo)定。在這個光強(qiáng)區(qū)間內(nèi)xe的電離曲線與ppt理論模擬的結(jié)果符合的很好,簡單化的勢壘抑制電離模型得到的飽和光強(qiáng)與ppt理論所給出的結(jié)果一致。對于kr在激光強(qiáng)度相對較低時的電離,實驗上觀測到了共振放大多光子電離的貢獻(xiàn)。利用獲得的準(zhǔn)直分子作為研究體系,在激光強(qiáng)度從1013w/cm2到1015w/cm2的范圍內(nèi)對準(zhǔn)直、隨機(jī)分布和反準(zhǔn)直的碘甲烷和溴甲烷分子的電離依存產(chǎn)額進(jìn)行測量,并將得到的結(jié)果與經(jīng)過修正的ppt理論模擬結(jié)果相對比,詳細(xì)分析觀測到不同光強(qiáng)區(qū)間內(nèi)homo和低層分子軌道對于電離過程的貢獻(xiàn)。對于較低光強(qiáng)下隨機(jī)分布的ch3br分子的電離產(chǎn)額,實驗測量結(jié)果與ppt理論預(yù)測結(jié)果存在偏差,我們將這部分偏差歸因于通過具有a1對稱性的軌道電離的貢獻(xiàn),這部分的貢獻(xiàn)可能來自于共振激發(fā)過程;當(dāng)激光強(qiáng)度相對較高時,電離主要是通過垂直于分子軸分布的e軌道(homo)的貢獻(xiàn)。碘甲烷分子的電離與ppt理論模擬結(jié)果符合的很好,其電離主要是通過e軌道(homo)發(fā)生。利用六極桿轉(zhuǎn)動態(tài)選擇技術(shù)與激光準(zhǔn)直技術(shù)的結(jié)合的這種方法實現(xiàn)了對電離過程中的不同軌道對于電離產(chǎn)額的貢獻(xiàn),即homo軌道和低層分子軌道的貢獻(xiàn)的探測。通過角度分辨光電子速度成像的實驗方法對準(zhǔn)直與反準(zhǔn)直的碘甲烷分子的多光子電離電子進(jìn)行了成像測量。通過光電子能譜隨光強(qiáng)的變化對電子能譜中的不同峰進(jìn)行了指認(rèn),在光強(qiáng)為9.6×1012 W/cm2下觀測到準(zhǔn)直與反準(zhǔn)直分子的電子能譜中兩個通道的分支比的不同,我們將其歸因于有效電離勢隨分子空間排列方向改變而改變所導(dǎo)致的。
[Abstract]:Taking the halogenated methane as an example, this paper studies the collimation behavior of molecules under the interaction of six polar electrostatic field and femtosecond laser field combined with experiment and theory, and discusses how to directly extract the average value of the two order Legendre polynomial of the molecular collimation degree parameter "P_2 (COS theta)" by the velocity imaging experimental data. A clear and systematic understanding of the mechanism of the kinetic mechanism of molecular rotation is obtained. Using the prepared collimator and the anti collimator, the ionization behavior of the halogenated methane molecules in the strong laser field is studied from different sides by the ion ionization yield measurement and the electron imaging experiment. The ionization process in the field is a hot spot in the field of strong field physics because of its quantum state complexity and multi particle association. Especially when the laser intensity is between the multiphoton ionization region and the tunneling ionization region, there are still many physical problems that have not been clearly explained. It is associated with the molecular coordinate system, which makes the study of strong field physics in the molecular coordinate system possible, and also requires the development of new experimental detection technology. We have developed a set of experimental device for electrostatic six pole combined with velocity imaging detection, and the dynamic selection through the six pole transfer. This experimental technique uses the electrostatic field and the molecular dipole. The stac effect between the moments can be obtained by a symmetric gyro halogenated methane molecule at the |1 + 1 (?) rotation quantum state. The molecule after selection is used by a linear femtosecond laser with a beam of 800 nm, the direction of polarization perpendicular to the time of the time of flight mass spectrometry, and is nonadiabatic collimation, and then the molecules are controlled. The line biased laser detection of second beams of delay in the same polarization direction. Theoretically we simulated the rotational wave packet structure of the iodide molecule at the |1 + 1 (?) 1 (?) 1 rotation in the vertical geometry of the collimated laser polarization vector perpendicular to the ion lens electrostatic field. The results of the theoretical simulation are reproduced by the rotational wave packet cycle shape of the measured ion signal. It can be seen that under the usual vertical geometric condition used in the velocity imaging device, the deviation of the ion corresponding to the Yu Chunzhu symmetry is negligible when the collimation laser is strong enough. The collimation parameter obtained by the theoretical simulation is obtained. The maximum and minimum positions in the rotational wave packet cycle correspond well with the collimation parameters extracted from the experimental results of the velocity imaging. In the experiment, the upper and lower limits of the controllable collimation degree of this laser can reach "P_2 (COS [theta) =0.7 and" P_2 (COS theta) =-0.1.. The writing of the PPT theory program has been completed and the writing of the PPT theory is completed. The test results are compared with the experimental results of the ionization yield of the inert gas Kr and Xe at the laser intensity from 1013w/cm2 to 1015w/cm2. The reliability of the PPT theoretical program and the calibration of the light intensity are verified. In this light intensity interval, the ionization curve of the Xe is in good agreement with the results of the PPT theory, and the simplification of the barrier is suppressed. The saturation light intensity obtained by the model ionization model is in agreement with the results given by the PPT theory. For the ionization of Kr at relatively low laser intensity, the contribution of the resonance amplification multiphoton ionization is observed experimentally. Using the obtained collimator as the research system, the laser intensity is collimated within the range of 1013w/ cm2 to 1015w/cm2, and the random distribution is distributed. The ionization dependent yield of the anti collimated iodide and methyl bromide molecules is measured, and the results are compared with the modified ppt theoretical simulation results. The contribution of the HOMO and the low molecular orbital to the ionization process in different light intensity ranges is analyzed in detail. The ionization of the random distribution of CH3Br molecules under the lower light intensity is analyzed. There is a deviation between the experimental results and the PPT theoretical prediction results. We attribute this partial deviation to the contribution of orbital ionization with A1 symmetry. The contribution of this part may come from the resonance excitation process; when the laser intensity is relatively high, the ionization is mainly through the contribution of the e orbit (Homo) perpendicular to the molecular axis. The ionization of iodide methane is in good agreement with the PPT theoretical simulation results, and its ionization mainly occurs through the e orbit (HOMO). The contribution of the different orbits to the ionization yield in the ionization process, namely the tribute of the Homo orbits and the low molecular orbital, is realized by the combination of the six pole transition dynamic selection technique and the laser collimation technique. An imaging measurement of the collimated and collimated multiphoton ionization electrons of iodide molecules by the angular resolution of the photoelectron velocity imaging. The different peaks in the electron spectrum are identified by the change of photoelectron spectroscopy with the change of light intensity. The collimation and collimation of the collimation and collimation are observed under the light intensity of 9.6 x 1012 W/cm2. The branching ratio of the two channels in the electron spectrum of the son is different. We attribute it to the change of the effective ionization potential with the change of the orientation of the molecular space.

【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2016
【分類號】：TN24;O561

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