We simulate the pump-probe experiments of lasing in molecular nitrogen ions with particular interest on the effects of rotational wave-packet dynamics. Our computations demonstrate that the coherent preparation of rotational wave packets in N${}_2^{+}$ by an intense short non-resonant pulse results in a modulation of the subsequent emission from $B^2{\Sigma }_u^{+}\to X^2{\Sigma }_g^{+}$ transitions induced by a resonant seed pulse. We model the dynamics of such pumping and emission using density matrix theory to describe the N${}_2^{+}$ dynamics and the Maxwell wave equation to model the seed pulse propagation. We show that the gain and absorption of a delayed seed pulse is dependent on the pump-seed delay, that is, the rotational coherences excited by the pump pulse can modulate the gain and absorption of the delayed seed pulse. Further, we demonstrate that the coherent rotational dynamics of the nitrogen ions can cause lasing without electronic inversion.

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N2 +激光：在旋转相干的情况下获得和吸收

我们模拟了对分子氮离子激射的泵浦探针实验，特别是对旋转波包动力学的影响。我们的计算证明了N中旋转波包的相干准备${}_2^{+}$ 短而强烈的非共振脉冲会导致随后的来自 ${乙}^2{\Sigma }_{ü}^{+}\to X^2{\Sigma }_G^{+}$由共振种子脉冲引起的跃迁。我们使用密度矩阵理论对此类抽运和排放的动力学进行建模，以描述N${}_2^{+}$动力学和麦克斯韦波方程来模拟种子脉冲传播。我们表明，延迟种子脉冲的增益和吸收取决于泵浦种子延迟，也就是说，由泵浦脉冲激发的旋转相干性可以调制延迟种子脉冲的增益和吸收。此外，我们证明了氮离子的相干旋转动力学可以引起激光发射而无需电子反转。