Department of Chemistry, Emory University, Atlanta, Georgia 30322, USA.
J Chem Phys. 2012 Dec 7;137(21):214313. doi: 10.1063/1.4768548.
Electronic spectra for BeC have been recorded over the range 30,500-40,000 cm(-1). Laser ablation and jet-cooling techniques were used to obtain rotationally resolved data. The vibronic structure consists of a series of bands with erratic energy spacings. Two-color photoionization threshold measurements were used to show that the majority of these features originated from the ground state zero-point level. The rotational structures were consistent with the bands of (3)Π-X(3)Σ(-) transitions. Theoretical calculations indicate that the erratic vibronic structure results from strong interactions between the four lowest energy (3)Π states. Adiabatic potential energy curves were obtained from dynamically weighted MRCI calculations. Diabatic potentials and coupling matrix elements were then reconstructed from these results, and used to compute the vibronic energy levels for the four interacting (3)Π states. The predictions were sufficiently close to the observed structure to permit partial assignment of the spectra. Bands originating from the low-lying 1(5)Σ(-) state were also identified, yielding a (5)Σ(-) to X(3)Σ(-) energy interval of 2302 ± 80 cm(-1) and molecular constants for the 1(5)Π state. The ionization energy of BeC was found to be 70,779(40) cm(-1).
已记录了范围在 30500-40000cm(-1) 的 BeC 的电子光谱。使用激光烧蚀和喷射冷却技术获得了旋转分辨数据。这些振子结构由一系列具有不规则能量间距的带组成。双色光电离阈测量用于表明，这些特征中的大多数源自基态零点水平。旋转结构与（3）Π-X（3）Σ(-)跃迁的带一致。理论计算表明，不规则的振子结构是由四个最低能量（3）Π态之间的强相互作用引起的。从动态加权 MRCI 计算中获得了绝热势能曲线。然后，从这些结果中重建了 diabatic 势能和耦合矩阵元，并用于计算四个相互作用的（3）Π态的振子能级。预测与观察到的结构足够接近，允许对光谱进行部分分配。还识别出源自低能 1（5）Σ(-)态的带，得到 1（5）Σ(-)到 X（3）Σ(-)的能量间隔为 2302 ± 80cm(-1)和 1（5）Π态的分子常数。BeC 的电离能被发现为 70779(40)cm(-1)。
