Giant Enhancement of Air Lasing by Complete Population Inversion in N2+
Giant Enhancement of Air Lasing by Complete Population Inversion in N2+
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DOI：
10.1103/physrevlett.125.053201
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发表时间：
2020-07-28
影响因子：
8.6
通讯作者：
Xu, Huailiang
中科院分区：
文献类型：
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作者：
Li, Hanxiao;Lotstedt, Erik;Xu, Huailiang
在分子量子能级之间对布居数转移进行精细操控是控制分子过程的一项关键技术。当光场强度增加到太瓦 - 拍瓦每平方厘米的水平时，通过非线性光 - 分子相互作用将布居数转移到特定激发能级成为可能，但控制布居数转移的程度一直是一个挑战。我们通过在氮气中聚焦双色（800纳米和1.6微米）强飞秒激光脉冲，几乎完全耗尽了N₂⁺的X²Σ⁺₍g₎（v = 0）态的布居数，并使391纳米处的N₂⁺激光强度提高了5 - 6个数量级。通过求解一个描述N₂⁺的三个最低电子态之间布居数转移的含时薛定谔方程，我们揭示了X²Σ⁺₍g₎（v = 0）布居数是通过振动拉曼激发以及随后的电子激发A²Πᵤ（v = 2,3,4）而被耗尽的。
A fine manipulation of population transfer among molecular quantum levels is a key technology for control of molecular processes. When a light field intensity is increased to the TW-PW cm(-2) level, it becomes possible to transfer a population to specific excited levels through nonlinear light-molecule interaction, but it has been a challenge to control the extent of the population transfer. We deplete the population in the X-2 Sigma(+)(g) (v = 0) state of N-2(+) almost completely by focusing a dual-color (800 nm and 1.6 mu m) intense femtosecond laser pulse in a nitrogen gas, and make the intensity of N-2(+) lasing at 391 nm enhanced by 5-6 orders of magnitude. By solving a time-dependent Schrodinger equation describing the population transfer among the three lowest electronic states of N-2(+), we reveal that the X-2 Sigma(+)(g) (v = 0) population is depleted by the vibrational Raman excitation followed by the electronic excitation A(2)Pi(u)(v = 2,3,4)