High-resolution spectroscopy of the C-N stretching band of methylamine
High-resolution spectroscopy of the C-N stretching band of methylamine
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DOI：
10.1063/1.3633699
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发表时间：
2011-09-14
影响因子：
4.4
通讯作者：
Billinghurst, B. E.
中科院分区：
文献类型：
--
作者：
Lees, Ronald M.;Sun, Zhen-Dong;Billinghurst, B. E.
用高分辨激光边带和傅里叶变换同步辐射光谱研究了CH_3NH_2分子的C-N伸缩红外基频，探讨了其能级结构，并寻找了与基态高扭能级及其它振动模的可能相互作用.该光谱是复杂的两个耦合的大振幅运动的分子，CH 3扭转和NH 2的反转，这导致丰富的光谱结构与宽范围的能级分裂和相对线强度。对于v（t）= 0扭转状态的较强的α反转物种，已经为K值分配了许多子带，范围高达12，沿着s物种的许多较弱的子带。用J（J + 1）幂级数展开式拟合上态项，确定了C-N伸缩子态的起源。为了与基态行为进行比较，地面和C-N拉伸起源已被安装到一个唯象的傅立叶级数模型，产生一个有趣的模式与不同的周期性的扭转和反转能量。扭转能量振荡的振幅对于C-N拉伸显著增加，而反转能量振荡的振幅相对不变。独立的惯性标度因子p适合的扭转和反转，并显着不同的上部状态。C-N伸缩振动能为1044.817 cm（-1），有效上态B值为0.7318 cm（-1）。几个非谐共振与v（t）= 4基态能级已被观察到，并部分表征。各种非本地化的能级交叉共振也被看到，其中五个显示禁止的强度借用，允许确定的相互作用耦合常数所产生的过渡。(C)2011年美国物理学会。[doi：10.1063/1.3633699]
The C-N stretching infrared fundamental of CH3NH2 has been investigated by high-resolution laser sideband and Fourier transform synchrotron spectroscopy to explore the energy level structure and to look for possible interactions with high-lying torsional levels of the ground state and other vibrational modes. The spectrum is complicated by two coupled large-amplitude motions in the molecule, the CH3 torsion and the NH2 inversion, which lead to rich spectral structure with a wide range of energy level splittings and relative line intensities. Numerous sub-bands have been assigned for K values ranging up to 12 for the stronger a inversion species for the v(t) = 0 torsional state, along with many of the weaker sub-bands of the s species. The C-N stretching sub-state origins have been determined by fitting the upper-state term values to J(J + 1) power-series expansions. For comparison with the ground-state behaviour, both ground and C-N stretch origins have been fitted to a phenomenological Fourier series model that produces an interesting pattern with the differing periodicities of the torsional and inversion energies. The amplitude of the torsional energy oscillation increases substantially for the C-N stretch, while the amplitude of the inversion energy oscillation is relatively unchanged. Independent inertial scale factors p were fitted for the torsion and the inversion and differ significantly in the upper state. The C-N stretching vibrational energy is determined to be 1044.817 cm(-1), while the effective upper state B-value is 0.7318 cm(-1). Several anharmonic resonances with v(t) = 4 ground-state levels have been observed and partially characterized. A variety off-localized level-crossing resonances have also been seen, five of which display forbidden transitions arising from intensity borrowing that allow determination of the interaction coupling constants. (C) 2011 American Institute of Physics. [doi:10.1063/1.3633699]