發(fā)布時間：2018-05-15 07:21

  本文選題：鋰原子 + 三步光激發(fā)　； 參考：《物理學報》2017年07期

【摘要】：原子能級的量子統(tǒng)計權重(G)是原子的重要光譜參數,但在研究原子的電離過程中通常卻為了簡化問題而被忽略.本文在鋰原子的三步光激發(fā)(PE)+電場電離(EFI)過程中計入了其影響,并發(fā)現其對原子EFI效率的影響顯著.本文精心設計了一套鋰原子的PE+EFI方案:首先,采用三臺不同波長的脈沖激光器分三步將原子從基態(tài)激發(fā)到某一Rydberg態(tài)上,經過一段時間延遲后再施加脈沖電場將其電離.針對原子所經歷的PE、零場和EFI這三個物理過程,本文對其物理機制進行了分析并建立了服從粒子數守恒的物理模型進而導出了顯含G參數的普適的速率方程組.其次,通過Matlab編程,分別針對精心選定的兩條激發(fā)路徑2S_(1/2)→2P_(1/2)→3S_(1/2)→25P_(1/2,3/2)和2S_(1/2)→2P_(3/2)→3D_(5/2)→25F_(5/2,7/2)開展了數值計算.研究發(fā)現:PE+EFI過程的總體效率的上限既與激光參數無關,也不依賴于G參數的絕對值,而是決定于Rydberg態(tài)的G參數的分支比.總之,通過精選激發(fā)路徑可以調控PE過程各相關態(tài)的布居率,并能適當提高PE+EFI過程的總電離效率,但卻因受到Rydberg態(tài)布居率的限制而很難進一步提高.
[Abstract]:The quantum statistical weight of atomic energy is an important spectral parameter of atoms, but it is usually neglected to simplify the process of atomic ionization. In this paper, the influence of the three-step photoexcited electron field ionization (EFI) of lithium atom is considered, and it is found that it has a significant effect on the atomic EFI efficiency. In this paper, a set of PE EFI scheme for lithium atoms is carefully designed. Firstly, three pulsed lasers of different wavelengths are used to excite the atoms from ground state to a certain Rydberg state in three steps, and then ionization them with a pulsed electric field after a period of delay. In this paper, the physical mechanism of PE-, zero-field and EFI processes experienced by atoms is analyzed, and a physical model of conservation of particle numbers is established, and then the universal rate equations with G parameters are derived. Secondly, through Matlab programming, numerical calculations were carried out for two carefully selected excitation paths, 2S / 1 / 2) 2P / 1 / 2) / 3s / 2) 25P, 1 / 2 / 2) and 2S / 1 / 2) 2P / 2) 2P / 2) 3 / 2) 3D / 5 / 2) 25F / 52 / 72). It is found that the upper limit of the total efficiency of the EFI process is not dependent on the laser parameters nor on the absolute value of the G parameters, but on the branching ratio of the G parameters of the Rydberg state. In a word, the population distribution of each dependent state in PE process can be controlled by the selective excitation path, and the total ionization efficiency of PE EFI process can be improved appropriately, but it is difficult to improve further because of the limitation of Rydberg distribution.
【作者單位】： 天津理工大學理學院;中國科學院武漢物理與數學研究所波譜與原子分子物理國家重點實驗室;
【基金】：國家自然科學基金(批準號:11174218)資助的課題~~
【分類號】：O562

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