The early transition metal diatomic sulfides, MS, M = Sc, Y, Ti, Zr, Hf, Nb, and Ta, have been investigated using resonant two-photon ionization spectroscopy in the vicinity of their bond dissociation energies (BDEs). Due to the high density of vibronic states in this energy range, the molecular spectra appear quasicontinuous, and when the excitation energy exceeds the ground separated atom limit, excited state decay by dissociation becomes possible. The dissociation process typically occurs so rapidly that the molecule falls apart before a second photon can be absorbed to ionize the species, leading to a sharp drop in ion signal, which is identified as the 0 K BDE. The observed predissociation thresholds yield BDEs of 4.852(10) eV (ScS), 5.391(3) eV (YS), 4.690(4) eV (TiS), 5.660(4) eV (ZrS), 5.780(20) eV (HfS), 5.572(3) eV (NbS), and 5.542(3) eV (TaS). Utilizing thermochemical cycles, the enthalpies of formation, Delta H-f(0K)o(g), of 182.7(4.3) kJ mol(-1) (ScS), 178.3(4.2) kJ mol(-1) (YS), 293.1(16.7) kJ mol(-1) (TiS), 337.3(8.4) kJ mol(-1) (ZrS), 335.0(6.6) kJ mol(-1) (HfS), 467.0(8.0) kJ mol(-1) (NbS), and 521.5(2.1) kJ mol(-1) (TaS) are obtained. Another thermochemical cycle has been used to combine the previously measured M+-S BDEs with the M-S BDEs and atomic ionization energies to obtain the MS ionization energies of 6.44(5) eV (ScS), 6.12(8) eV (YS), 6.78(7) eV (TiS), 6.60(10) eV (ZrS), and 6.88(9) eV (NbS). Using this same cycle, we obtain D-0(Hf+-S) = 4.926(20) eV. The bonding trends of the early transition metal sulfides, along with the corresponding selenides, are discussed.
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机译:利用共振双光子电离光谱研究了早期过渡金属双原子硫化物MS、M = Sc、Y、Ti、Zr、Hf、Nb和Ta的键解离能(BDE)附近。由于该能量范围内振动态的高密度,分子光谱呈现准连续,当激发能量超过基分离原子极限时,通过解离使激发态衰变成为可能。解离过程通常发生得如此之快,以至于分子在吸收第二个光子以电离物质之前就分崩离析,导致离子信号急剧下降,这被确定为0 K BDE。观察到的预解离阈值产生的溴化二苯醚为4.852(10) eV (ScS)、5.391(3) eV (YS)、4.690(4) eV (TiS)、5.660(4) eV (ZrS)、5.780(20) eV (HfS)、5.572(3) eV (NbS) 和 5.542(3) eV (TaS)。利用热化学循环,得到的生成焓Delta H-f(0K)o(g)为182.7(4.3) kJ mol(-1) (ScS)、178.3(4.2) kJ mol(-1) (YS)、293.1(16.7) kJ mol(-1) (TiS)、337.3(8.4) kJ mol(-1) (ZrS)、335.0(6.6) kJ mol(-1) (HfS)、467.0(8.0) kJ mol(-1) (NbS) 和 521.5(2.1) kJ mol(-1) (TaS).另一个热化学循环用于将先前测量的M+-S BDEs与M-S BDEs和原子电离能相结合,以获得6.44(5) eV(ScS)、6.12(8) eV(YS)、6.78(7) eV(TiS)、6.60(10) eV (ZrS) 和 6.88(9) eV (NbS) 的 MS 电离能。使用相同的循环,我们得到 D-0(Hf+-S) = 4。926(20) 电子伏。讨论了早期过渡金属硫化物以及相应的硒化物的键合趋势。
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