Vibrational modes of the relatively strongly bound H₂He⁺ molecular ion and its deuterated congener D₂He⁺ are investigated by low-resolution multi-photon photodissociation spectroscopy, using a combination of a 4 K cryogenic ion-trap machine and the free-electron-laser FELIX. The band origins obtained are fully explained by accurate variational calculations of the rovibrational states of H₂He⁺ and D₂He⁺ based on the three-dimensional potential energy surface of Koner et al. (2019). Results from second-order vibrational perturbation theory, based on a linear H–H–He equilibrium structure, agree well with those of the variational calculations for energies up to about 1300 cm⁻¹. This suggests that H₂He⁺ and D₂He⁺ may either be considered as linear triatomic molecules with a degenerate bending mode, or as Van der Waals complexes with a strongly hindered rotation of He around the ${\mathrm{H}}_2^{+}$ and ${\mathrm{D}}_2^{+}$ subunits. The variational calculations show that in states close to the dissociation limit, 1794 and 1852 cm⁻¹ for para- and ortho-H₂He⁺, respectively, the angular internal motion becomes delocalized. The low-resolution experiments corroborate the linear structure of the ions and identify the bright IR-active HH-stretch fundamental in H₂He⁺ at about 1840 cm⁻¹ and the DD-stretch fundamental in D₂He⁺ at about 1309 cm⁻¹, both with an uncertainty of 0.5%, in good agreement with the calculations. The experiments also confirm the ${\mathrm{H}}_2^{+}$–He bend and stretch fundamentals calculated at 632 and 732 cm⁻¹ and the ${\mathrm{D}}_2^{+}$–He bend and stretch fundamentals at 473 and 641 cm⁻¹, respectively.

结合使用4 K低温离子阱仪和自由电子，通过低分辨率多光子光解离光谱研究了相对强结合的H ₂ He ⁺分子离子及其氘代同系物D ₂ He ^+的振动模式。-激光FELIX。通过对H ₂ He ⁺和D ₂ He ⁺的旋转振动态进行精确的变分计算，可以充分说明获得的谱带起源。基于Koner等人的三维势能面。（2019）。基于线性H–H–He平衡结构的二阶振动摄动理论的结果与大约1300 cm ^-1的能量的变分计算结果非常吻合。这表明H ₂ He ⁺和D ₂ He ⁺可以被认为是具有简并弯曲模式的线性三原子分子，也可以被视为Van der Waals络合物，其中He强烈地绕着H ₂ He旋转。${\mathrm{H}}_{\mathrm{2个}}^{+}$ 和 ${\mathrm{d}}_{\mathrm{2个}}^{+}$亚单位。变分计算表明，在接近解离极限的状态下，对-H ₂ He ⁺和邻-H ₂ He ⁺分别为1794和1852 cm ^-1，角内运动变得离域。低分辨率实验证实了离子的线性结构，并在大约1840 cm ^-1的H ₂ He ⁺中确定了明亮的IR活性HH拉伸基数，在大约1309 cm-的D ₂ He ⁺中识别了DD拉伸基数^{。 1}，二者的不确定度均为0.5％，与计算结果非常吻合。实验还证实了${\mathrm{H}}_{\mathrm{2个}}^{+}$–他弯曲并拉伸在632和732 cm ^-1处计算的基本面，并且${\mathrm{d}}_{\mathrm{2个}}^{+}$–他分别在473和641 cm ^-1处弯曲和拉伸基本面。