Faculty of Information Sciences, Hiroshima City University, Hiroshima 731-3194, Japan.
J Chem Phys. 2011 Sep 28;135(12):124311. doi: 10.1063/1.3640024.
We have generated MgNC in supersonic free jet expansions and observed the laser induced fluorescence (LIF) of the Ã(2)Π-X̃(2)Σ(+) transition. We measured the LIF dispersed spectra from the single vibronic levels of the Ã(2)Π electronic state of MgNC, following excitation of each ν(2) bending vibronic band observed, i.e., the κ series of the (0,v(2)('),0)-(0,0,0), v(2)(') = 0, 1, 2, 4, and 6 vibronic bands. In the vibrational structure in the dispersed fluorescence spectra measured, the long progression of the ν(2) bending mode in the X̃(2)Σ(+) state is identified, e.g., up to v(2)('')=14 in the (0,6,0)-(0,v(2)(''),0) spectrum. This enables us to derive the potential curve of the ν(2) bending mode in the X̃(2)Σ(+) state. We used two kinds of models to obtain the potential curve; (I) the customary formula expressed in the polynomial series of the (v(2)('')+(d(2)/2)) term and (II) the internal rotation model. The potential curve derived from model (I) indicates the convergence of the bending vibrational levels at about 800 cm(-1) from the vibrationless level of MgNC, which may correspond to the barrier height of the isomerization reaction, MgNC ⇌ MgCN, in the X̃(2)Σ(+) state. Model (II) gives a simple picture for the isomerization reaction pathway with a barrier height of about 630 cm(-1) from the vibrationless level of the more stable species, MgNC. This shows that the v(2)('')=8 bending vibrational level of MgNC is already contaminated by the v(2)('')=2 bending vibrational level of the isomer, MgCN, and implies that the isomerization reaction begins at the v(2) ('')=8 level. The bending potential surface and the isomerization reaction pathway, MgNC ⇌ MgCN, in the X̃(2)Σ(+) state are discussed by comparing the potential derived in this study with the surface obtained by quantum chemical calculation.
我们在超声速自由喷射膨胀中生成了 MgNC，并观察到了Ã(2)Π-X̃(2)Σ(+)跃迁的激光诱导荧光（LIF）。我们测量了Ã(2)Π电子态的单振动态的 LIF 分散光谱，这些振动态是通过激发观察到的每个ν(2)弯曲振动态带得到的，即（0，v(2)(')，0）-（0，0，0）的κ系列的（0，v(2)(')，0），v(2)(') = 0、1、2、4 和 6 振动态带。在测量的分散荧光光谱中的振动结构中，识别出 X̃(2)Σ(+)态中 ν(2)弯曲模式的长级联，例如，在（0，6，0）-（0，v(2)(')，0）光谱中高达 v(2)(''')=14。这使我们能够推导出 X̃(2)Σ(+)态中 ν(2)弯曲模式的势能曲线。我们使用两种模型来获得势能曲线;（I）用（v(2)(''')+(d(2)/2)）项表示的常规多项式级数公式和（II）内部旋转模型。由模型（I）得到的势能曲线表明，在距 MgNC 的无振动能级约 800 cm(-1)处，弯曲振动能级收敛，这可能对应于 X̃(2)Σ(+)态中异构化反应 MgNC ⇌ MgCN 的势垒高度。模型（II）给出了一个简单的异构化反应途径图，其势垒高度约为更稳定物质 MgNC 的无振动能级的 630 cm(-1)。这表明 MgNC 的 v(2)(''')=8 弯曲振动能级已经被异构体 MgCN 的 v(2)(''')=2 弯曲振动能级污染，这意味着异构化反应开始于 v(2)(''')=8 能级。通过将本研究中得到的势能与量子化学计算得到的表面进行比较，讨论了 X̃(2)Σ(+)态中 MgNC 的弯曲势能面和异构化反应途径 MgNC ⇌ MgCN。
