Tomchak Kimberly H, Sorensen Jason J, Tieu Erick, Morse Michael D
Department of Chemistry, University of Utah, Salt Lake City, Utah 84112-0850, USA.
J Chem Phys. 2024 Jul 28;161(4). doi: 10.1063/5.0220813.
The uranium-containing molecules US2, OUS, and USe have been investigated using a pulsed laser ablation supersonic beam molecular source with time-of-flight mass spectrometric detection. Spectra have been recorded using the resonant two-photon ionization method over the spectroscopic range from 277 to 238 nm. These species have a myriad of excited electronic states in this spectroscopic region, leading to spectra that are highly congested and appear quasicontinuous. Sharp predissociation thresholds are observed, allowing precise bond dissociation energies to be measured. In the case of the triatomic molecules, it was necessary to use one laser for excitation and a delayed laser for ionization in order to observe a sharp predissociation threshold that allowed a precise bond dissociation energy to be measured. The resulting thermochemical values are D0(SU-S) = 4.910 ± 0.003 eV, D0(OU-S) = 5.035 ± 0.004 eV, and D0(USe) = 4.609 ± 0.009 eV. These results provide the first measurement of D0(USe) and reduce the error limits in the previous values of D0(SU-S) and D0(OU-S) by a factor of more than 70.
已使用脉冲激光烧蚀超声分子束源结合飞行时间质谱检测对含铀分子US2、OUS和USe进行了研究。在277至238纳米的光谱范围内，采用共振双光子电离法记录了光谱。这些物质在该光谱区域有大量的激发电子态，导致光谱高度拥挤且呈现准连续状态。观察到了尖锐的预解离阈值，从而能够精确测量键解离能。对于三原子分子，为了观察到能精确测量键解离能的尖锐预解离阈值，需要使用一台激光器进行激发，并用一台延迟激光器进行电离。得到的热化学值为D0(SU - S)=4.910±0.003电子伏特，D0(OU - S)=5.035±0.004电子伏特，以及D0(USe)=4.609±0.009电子伏特。这些结果首次测量了D0(USe)，并将先前D0(SU - S)和D0(OU - S)值的误差范围缩小了70多倍。
