本文選題：冷靶反沖離子動(dòng)量譜儀　切入點(diǎn)：少周期飛秒激光脈沖　出處：《中國科學(xué)院研究生院(武漢物理與數(shù)學(xué)研究所)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：隨著激光技術(shù)的發(fā)展,特別是超短激光脈沖的出現(xiàn),激光與物質(zhì)相互作用進(jìn)入一個(gè)全新的領(lǐng)域。用飛秒脈沖光作為轟擊粒子與目標(biāo)粒子相互作用,如果能夠掌握作用前后粒子的狀態(tài)信息,就可以實(shí)現(xiàn)原子分子內(nèi)部電子動(dòng)力學(xué)的飛秒超快測量。本論文基于冷靶反沖離子動(dòng)量譜儀(COLTRIMS)結(jié)合載波-包絡(luò)相位穩(wěn)定的周期量級(jí)飛秒激光器系統(tǒng),系統(tǒng)的開展了氫分子在少周期激光場下的雙電離動(dòng)力學(xué)行為研究,以及原子電離過程中載波-包絡(luò)相位效應(yīng)研究。主要內(nèi)容如下：1.自主建設(shè)了一套用于原子分子超快動(dòng)力學(xué)研究的COLTRIMS系統(tǒng)。其主要包括三個(gè)部分,真空系統(tǒng),超聲分子束和離子電子動(dòng)量測量系統(tǒng)。文中分別對(duì)各個(gè)部分的搭建過程和工作原理進(jìn)行了闡述。完成后的COLTRIMS在真空度、分子束冷卻溫度和離子電子探測系統(tǒng)的測量范圍和精度都達(dá)到國際先進(jìn)水平,為開展原子分子內(nèi)部超快動(dòng)力學(xué)的研究奠定了堅(jiān)實(shí)基礎(chǔ)。2.實(shí)驗(yàn)上研究了氫分子在超短脈沖激光場驅(qū)動(dòng)下的雙電離動(dòng)力學(xué)行為。雙電離過程中產(chǎn)生的兩個(gè)質(zhì)子的動(dòng)能釋放譜,可以用于分辨導(dǎo)致雙電離的不同通道。通過測量不同激光參數(shù)(如激光強(qiáng)度,激光偏振和脈沖寬度)下的動(dòng)能釋放譜,結(jié)果顯示在長脈沖激光場下(即25 fs),主要有兩種路徑導(dǎo)致雙電離,即電荷共振增強(qiáng)電離和重碰撞導(dǎo)致的雙電離。另外,可以通過改變激光脈沖的光強(qiáng)來調(diào)控這兩個(gè)過程。而在5 fs激光脈沖下,只有重碰撞導(dǎo)致的雙電離過程存在,特別是這一過程只有來自第一次返回軌道重碰撞導(dǎo)致的雙電離通道,利用如此短的脈沖為研究亞周期尺度的分子動(dòng)力學(xué)提供一個(gè)有效的手段。3.分別從實(shí)驗(yàn)上和理論上研究少周期激光脈沖下原子電離過程中的載波-包絡(luò)相位效應(yīng)。實(shí)驗(yàn)上,通過測量不同載波-包絡(luò)相位下氬一價(jià)離子和氬二價(jià)離子的動(dòng)量分布,展示離子左右出射不對(duì)稱性系數(shù)隨載波-包絡(luò)相位的變化曲線是簡單的正弦函數(shù)振蕩。更有趣的是隨著激光光強(qiáng)的增加一價(jià)離子的不對(duì)稱性曲線相對(duì)右移,另外二價(jià)離子的不對(duì)稱性曲線與一價(jià)離子的不對(duì)稱性曲線之間的相移也會(huì)隨著光強(qiáng)的增加而發(fā)生變化。理論上,我們使用半經(jīng)典理論、SFA理論和CVA理論系統(tǒng)模擬了原子單電離過程中的載波-包絡(luò)相位效應(yīng)。通過對(duì)比不同理論模擬的結(jié)果,發(fā)現(xiàn)CVA理論可以定性重復(fù)實(shí)驗(yàn)結(jié)果。通過比較CVA理論與SFA理論模擬的結(jié)果,發(fā)現(xiàn)庫侖勢影響光電子發(fā)射的左右不對(duì)稱性,導(dǎo)致CVA理論與SFA理論模擬的結(jié)果不一致以及不同光強(qiáng)下不對(duì)稱性系數(shù)隨載波-包絡(luò)相位的變化曲線的相移。在Simple man模型下,闡明上述結(jié)果是由于庫侖勢對(duì)前向散射電子的明顯影響而造成的。
[Abstract]:With the development of laser technology, especially the emergence of ultrashort laser pulses, the interaction between laser and matter has entered a new field. If you can grasp the state of the particles before and after the action, In this paper, a periodic femtosecond laser system based on cold target recoil ion momentum spectrometer (COLTRIMS) and carrier envelope phase stability can be realized. The double ionization dynamics of hydrogen molecules in a small period laser field has been studied systematically. The main contents are as follows: 1. A set of COLTRIMS system for the study of ultrafast dynamics of atoms and molecules has been built. The system consists of three parts: vacuum system. Ultrasonic molecular beam and ion electron momentum measurement system. The construction process and working principle of each part are described in this paper. The vacuum degree of the finished COLTRIMS is obtained. The measurement range and accuracy of the molecular beam cooling temperature and ion electron detection system have reached the international advanced level. 2. The double ionization kinetics of hydrogen molecules driven by ultrashort pulse laser field is studied experimentally. The kinetic energy release spectra of two protons produced in the process of double ionization are studied. Can be used to identify different channels leading to double ionization. By measuring kinetic energy release spectra at different laser parameters, such as laser intensity, laser polarization, and pulse width, The results show that there are two main paths leading to double ionization under long pulse laser field (i.e. 25fsN), namely charge resonance enhanced ionization and double ionization caused by heavy collision. These two processes can be regulated by changing the light intensity of the laser pulse. In the case of a 5 fs laser pulse, only double ionization processes caused by heavy collisions exist. In particular, this process comes only from the double ionization channels resulting from the first re-entry orbit heavy collision, The use of such short pulses provides an effective means for studying subperiodic scale molecular dynamics. 3. The carrier envelope phase effect in the atomic ionization process under a small period laser pulse is studied experimentally and theoretically. The momentum distributions of argon monovalent ions and argon bivalent ions at different carrier envelope phases were measured. It is shown that the variation curve of ion left and right emission asymmetry coefficient with carrier envelope phase is a simple sinusoidal oscillation. More interesting is the relative right shift of the asymmetry curve with the increase of laser intensity. In addition, the phase shift between the asymmetry curve of bivalent ions and that of monovalent ions also changes with the increase of light intensity. We use semiclassical theory and CVA theory to simulate the carrier envelope phase effect in atomic mono ionization process. It is found that the CVA theory can qualitatively repeat the experimental results. By comparing the results of CVA theory and SFA theory, it is found that Coulomb potential affects the left and right asymmetry of photoelectron emission. The results of the simulation of CVA theory and SFA theory are inconsistent, and the phase shift of asymmetry coefficient with carrier envelope phase under different light intensities. In the Simple man model, It is shown that these results are due to the obvious influence of Coulomb potential on the forward scattering electrons.
【學(xué)位授予單位】：中國科學(xué)院研究生院(武漢物理與數(shù)學(xué)研究所)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：O437

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