利用整形激光脈沖控制原子光締合動力學(xué)及碰撞過程中電荷轉(zhuǎn)移
發(fā)布時間：2018-12-27 18:50
【摘要】：利用激光脈沖控制原子的光締合和碰撞過程中的電荷轉(zhuǎn)移是當(dāng)前原子與分子物理研究領(lǐng)域的兩個熱點(diǎn)研究方向。本論文在理論上研究了利用整形脈沖激光調(diào)控碰撞原子光締合及電荷轉(zhuǎn)移過程。主要工作概括如下： (1)提出了利用整形脈沖提高超冷原子光締合幾率的理論方案。通過求解兩態(tài)薛定諤方程,我們發(fā)現(xiàn)：具有緩慢打開、迅速關(guān)閉特性的激光脈沖在達(dá)到峰值強(qiáng)度之后,能夠減少激光與分子的能量交換,進(jìn)而阻止激發(fā)電子態(tài)的光締合分子解離回到基電子態(tài)的散射態(tài)上,達(dá)到提高光締合效率的效果。光締合幾率隨著脈沖關(guān)閉時間的縮短而增大。在此基礎(chǔ)上,還利用整形脈沖鏈的布居累積效應(yīng)提高光締合幾率。 (2)從理論上研究了利用調(diào)制脈沖來控制超冷原子的光締合動力學(xué)過程。研究結(jié)果表明,含時電場的形狀和頻譜分布對包絡(luò)相位很敏感。當(dāng)包絡(luò)周期大于脈沖的半高全寬時,光譜強(qiáng)度分布可以通過改變包絡(luò)相位修正。相關(guān)振動態(tài)的富蘭克-康登(Frank-Condon)因子、激光脈沖的頻譜強(qiáng)度分布以及激光場的時域不對稱性均影響光締合分子的振動態(tài)布居分布和光締合效率。 (3)從理論上研究了采用三階相位皮秒脈沖控制超冷原子的光締合動力學(xué)過程。三階相位脈沖由于延長了時域上的延續(xù)時間而增加了脈沖面積,因而增加了光締合效率。盡管當(dāng)脈沖面積一定時,三階相位脈沖的能量較低,但當(dāng)脈沖面積大于某個值時,卻能明顯提高光締合效率。與高斯脈沖相比,三階相位脈沖無法改變布居的振動態(tài)分布范圍,因?yàn)樗鼈兣c高斯脈沖的光譜分布相同。 (4)采取優(yōu)化控制理論,利用基電子態(tài)的一個較高振動態(tài),把光締合形成的外勢阱中的分子轉(zhuǎn)移到內(nèi)勢阱的一個振動態(tài)上。這要求優(yōu)化脈沖的頻譜足夠?qū)?能夠覆蓋初始態(tài)和目標(biāo)態(tài)的能級差。由優(yōu)化脈沖產(chǎn)生的激發(fā)態(tài)內(nèi)勢阱中布居可以用一束高斯脈沖完全轉(zhuǎn)移到基電子態(tài)的較低振動能級上。 (5)基于兩態(tài)絕熱表象,從理論上研究了優(yōu)化激光控制慢碰撞H++D中的電荷轉(zhuǎn)移過程。在沒有外場情況下,通過非絕熱耦合得到的電荷轉(zhuǎn)移幾率較低,而在優(yōu)化控制方案中,利用自由態(tài)與多個振動態(tài)之間的躍遷,幾乎100%控制電荷轉(zhuǎn)移。我們采用了兩種不同的目標(biāo)態(tài)來獲取優(yōu)化激光場：能夠進(jìn)行自我調(diào)節(jié)的目標(biāo)態(tài)(自適應(yīng)目標(biāo)態(tài))更加高效,但得到的電荷轉(zhuǎn)移后的波包結(jié)構(gòu)很復(fù)雜；固定目標(biāo)態(tài)收斂得更慢些,但可以得到與設(shè)定目標(biāo)完全匹配的波包。
[Abstract]:Controlling the photoassociation of atoms and the charge transfer during collisions by using laser pulses are two hot research directions in the field of atomic and molecular physics. In this paper, the photoassociation and charge transfer processes of collisional atoms controlled by plastic pulse laser are studied theoretically. The main works are summarized as follows: (1) A theoretical scheme to improve the photoassociation probability of ultracold atoms by shaping pulses is proposed. By solving the two-state Schrodinger equation, we find that the laser pulse with the characteristics of slow opening and quick closing can reduce the energy exchange between the laser and the molecule after the peak intensity is reached. Furthermore, the dissociation of the photoassociating molecules excited by the electron state is prevented from returning to the scattering state of the base electronic state, so that the photoassociation efficiency can be improved. The photoassociation probability increases with the shortening of pulse closing time. On this basis, the population accumulation effect of plastic pulse chain is used to improve the probability of photoassociation. (2) the photoassociation kinetics of ultracold atoms controlled by modulated pulses is studied theoretically. The results show that the shape and spectrum distribution of the time-dependent electric field are sensitive to the envelope phase. When the envelope period is larger than the full width of the pulse, the spectral intensity distribution can be corrected by changing the envelope phase. The Frank-Condon factor, the spectral intensity distribution of the laser pulse and the time-domain asymmetry of the laser field all affect the dynamic population distribution and the photoassociation efficiency of the photoassociated molecules. (3) the photoassociation kinetics of ultracold atoms controlled by third-order picosecond pulses is studied theoretically. The third order phase pulse increases the pulse area by prolonging the duration of time domain, thus increasing the photoassociation efficiency. Although the energy of the third order phase pulse is low when the pulse area is constant, the photoassociation efficiency can be improved obviously when the pulse area is larger than a certain value. Compared with Gao Si pulse, the third-order phase pulse can not change the dynamic distribution range of population, because they are the same spectral distribution as Gao Si pulse. (4) by using the optimal control theory, the molecules in the external potential well formed by photoassociation are transferred to a vibration state of the inner potential well by using a higher vibration state of the base electronic state. This requires that the spectrum of the optimized pulse be wide enough to cover the energy difference between the initial state and the target state. The population in the excited state generated by the optimized pulse can be completely transferred to the lower vibrational energy level of the base electronic state by a beam of Gao Si pulses. (5) based on the two-state adiabatic representation, the charge transfer process in the optimized laser controlled slow collision H D is studied theoretically. In the case of no external field, the probability of charge transfer obtained by non-adiabatic coupling is lower. In the optimal control scheme, almost 100% of the transition between free state and multiple vibration dynamics is used to control the charge transfer. We adopt two different target states to obtain the optimized laser field: the self-adjusting target state (adaptive target state) is more efficient, but the wavepacket structure after charge transfer is very complex; The fixed target state converges more slowly, but a wave packet that exactly matches the target setting can be obtained.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：O562
本文編號：2393465
[Abstract]:Controlling the photoassociation of atoms and the charge transfer during collisions by using laser pulses are two hot research directions in the field of atomic and molecular physics. In this paper, the photoassociation and charge transfer processes of collisional atoms controlled by plastic pulse laser are studied theoretically. The main works are summarized as follows: (1) A theoretical scheme to improve the photoassociation probability of ultracold atoms by shaping pulses is proposed. By solving the two-state Schrodinger equation, we find that the laser pulse with the characteristics of slow opening and quick closing can reduce the energy exchange between the laser and the molecule after the peak intensity is reached. Furthermore, the dissociation of the photoassociating molecules excited by the electron state is prevented from returning to the scattering state of the base electronic state, so that the photoassociation efficiency can be improved. The photoassociation probability increases with the shortening of pulse closing time. On this basis, the population accumulation effect of plastic pulse chain is used to improve the probability of photoassociation. (2) the photoassociation kinetics of ultracold atoms controlled by modulated pulses is studied theoretically. The results show that the shape and spectrum distribution of the time-dependent electric field are sensitive to the envelope phase. When the envelope period is larger than the full width of the pulse, the spectral intensity distribution can be corrected by changing the envelope phase. The Frank-Condon factor, the spectral intensity distribution of the laser pulse and the time-domain asymmetry of the laser field all affect the dynamic population distribution and the photoassociation efficiency of the photoassociated molecules. (3) the photoassociation kinetics of ultracold atoms controlled by third-order picosecond pulses is studied theoretically. The third order phase pulse increases the pulse area by prolonging the duration of time domain, thus increasing the photoassociation efficiency. Although the energy of the third order phase pulse is low when the pulse area is constant, the photoassociation efficiency can be improved obviously when the pulse area is larger than a certain value. Compared with Gao Si pulse, the third-order phase pulse can not change the dynamic distribution range of population, because they are the same spectral distribution as Gao Si pulse. (4) by using the optimal control theory, the molecules in the external potential well formed by photoassociation are transferred to a vibration state of the inner potential well by using a higher vibration state of the base electronic state. This requires that the spectrum of the optimized pulse be wide enough to cover the energy difference between the initial state and the target state. The population in the excited state generated by the optimized pulse can be completely transferred to the lower vibrational energy level of the base electronic state by a beam of Gao Si pulses. (5) based on the two-state adiabatic representation, the charge transfer process in the optimized laser controlled slow collision H D is studied theoretically. In the case of no external field, the probability of charge transfer obtained by non-adiabatic coupling is lower. In the optimal control scheme, almost 100% of the transition between free state and multiple vibration dynamics is used to control the charge transfer. We adopt two different target states to obtain the optimized laser field: the self-adjusting target state (adaptive target state) is more efficient, but the wavepacket structure after charge transfer is very complex; The fixed target state converges more slowly, but a wave packet that exactly matches the target setting can be obtained.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：O562
【參考文獻(xiàn)】
相關(guān)期刊論文 前2條
1 冉玲苓;曲士良;郭忠義;;Surface mico-structures on amorphous alloys induced by vortex femtosecond laser pulses[J];Chinese Physics B;2010年03期
2 周勇;苗泉;王傳奎;;Effect of Lorentz local field correction on propagation of ultrashort laser pulse in one-dimensional para-nitroaniline (PNA) molecules[J];Chinese Physics B;2011年04期
，本文編號：2393465
本文鏈接：http://sikaile.net/shoufeilunwen/jckxbs/2393465.html
最近更新
教材專著
