Here we report the dissociative ionization imaging of electronically excited nitric oxide (NO) molecules to visualize rotational wave functions in the electronic excited state (A ²Σ⁺). The NO molecules were excited to a single rotational energy eigenstate in the first electronic excited state by a resonant nanosecond ultraviolet pulse. The molecules were then irradiated by a strong, circularly polarized femtosecond imaging pulse. Spatial distribution of the ejected N⁺ and O⁺ fragment ions from the dissociative NO²⁺ was recorded as a direct measure of the molecular axis distribution using a high-resolution slice ion imaging apparatus. The circularly polarized probe pulse realizes the isotropic ionization and thus undistorted shapes of the functions can be visualized. Due to the higher ionization efficiency of the excited molecules relative to the ground state ones, signals from the excited NO were enhanced. We can, therefore, extract shapes of the square of rotational wave functions in the electronic excited state although the unexcited ground state molecules are the majority in an ensemble. The observed images show s-function-like and p-function-like shapes depending on the excitation wavelengths. These shapes well reflect the rotational (angular momentum) character of the prepared states. The present approach directly leads to the evaluation method of the molecular axis alignment in photo-excited ensembles, and it could also lead to a visualization method for excited state molecular dynamics.

中文翻译：

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通过使用离子成像技术可视化电子激发的一氧化氮分子的旋转波函数

这里，我们报告电子激发一氧化氮（NO）分子的解离性离子化成像在电子激发态的可视化旋转波函数（A ² Σ ⁺）。通过共振纳秒紫外脉冲，在第一电子激发态下，NO分子被激发成单一的旋转能本征态。然后，用强圆偏振飞秒成像脉冲照射分子。从解离性NO ²⁺喷射的N ⁺和O ⁺碎片离子的空间分布使用高分辨率切片离子成像设备记录的X射线衍射作为分子轴分布的直接量度。圆极化的探测脉冲实现了各向同性的电离，因此可以看到功能的未失真形状。由于被激发分子相对于基态分子具有更高的电离效率，来自被激发NO的信号得以增强。因此，我们可以在电子激发态中提取旋转波函数平方的形状，尽管在整体中未激发的基态分子占多数。观察到的图像取决于激发波长而显示出类似于s函数和p函数的形状。这些形状很好地反映了准备好的状态的旋转（角动量）特性。