本文選題：鋰原子 + 三步光激發(fā)�。� 參考：《物理學(xué)報(bào)》2017年07期

【摘要】：原子能級的量子統(tǒng)計(jì)權(quán)重(G)是原子的重要光譜參數(shù),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(jì)入了其影響,并發(fā)現(xiàn)其對原子EFI效率的影響顯著.本文精心設(shè)計(jì)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(jīng)過一段時(shí)間延遲后再施加脈沖電場將其電離.針對原子所經(jīng)歷的PE、零場和EFI這三個(gè)物理過程,本文對其物理機(jī)制進(jìn)行了分析并建立了服從粒子數(shù)守恒的物理模型進(jìn)而導(dǎo)出了顯含G參數(shù)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(shù)值計(jì)算.研究發(fā)現(xiàn):PE+EFI過程的總體效率的上限既與激光參數(shù)無關(guān),也不依賴于G參數(shù)的絕對值,而是決定于Rydberg態(tài)的G參數(shù)的分支比.總之,通過精選激發(fā)路徑可以調(diào)控PE過程各相關(guān)態(tài)的布居率,并能適當(dāng)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(jìn)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(xué)理學(xué)院;中國科學(xué)院武漢物理與數(shù)學(xué)研究所波譜與原子分子物理國家重點(diǎn)實(shí)驗(yàn)室;
【基金】：國家自然科學(xué)基金(批準(zhǔn)號:11174218)資助的課題~~
【分類號】：O562

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