Threshold photodetachment spectroscopy has been performed on the molecular anion CN⁻ at both 16(1) K and 295(2) K in a 22-pole ion trap and at 295(2) K from a pulsed ion beam. The spectra show a typical energy dependence of the detachment cross section yielding a determination of the electron affinity of CN to greater precision than has previously been known at 31 163(16) cm⁻¹ [3.864(2) eV]. Allowed s-wave detachment is observed for CN⁻, but the dependence of the photodetachment cross section near the threshold is perturbed by the long-range interaction between the permanent dipole moment of CN and the outgoing electron. Furthermore, we observe a temperature dependence of the cross section near the threshold, which we attribute to a reduction of the effective permanent dipole due to higher rotational excitation at higher temperatures.

中文翻译：

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天体化学阴离子 CN− 的阈值光分离光谱

已对分子阴离子 CN ^-在 22 极离子阱中的 16(1) K 和 295(2) K 以及脉冲离子束中的 295(2) K 进行了阈值光分离光谱。光谱显示了分离横截面的典型能量依赖性，从而确定了 CN 的电子亲和力，其精度高于之前已知的 31 163(16) cm -1 [3.864(2) ^eV ]。对于 CN 观察到允许的s波脱离^-，但阈值附近的光分离截面的依赖性受到 CN 的永久偶极矩与出射电子之间的长程相互作用的干扰。此外，我们观察到阈值附近横截面的温度依赖性，我们将其归因于由于在较高温度下较高的旋转激发而导致的有效永久偶极子的减少。