Matrix isolation spectroscopy and nuclear spin conversion of NH3 and ND3 in solid parahydrogen.
Matrix isolation spectroscopy and nuclear spin conversion of NH3 and ND3 in solid parahydrogen.
复制标题
固体仲氢中 NH3 和 ND3 的基质隔离光谱和核自旋转化。
DOI：
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发表时间：
2013
影响因子：
2.9
通讯作者：
David T. Anderson
中科院分区：
文献类型：
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作者：
M. Ruzi;David T. Anderson
本文报道了在1.8K左右，NH_3和ND_3在固体仲氢（pH_2）中的基质隔离红外吸收光谱。我们使用相对较慢的NH3和ND 3在新鲜沉积的pH 2样品的核自旋转换（NSC）作为一种工具，分配稀疏的振动反转旋转（VIR）光谱的NH3的区域的ν2，ν4，2ν4，ν1，和ν3带和ND 3的区域的ν 2，ν4，ν 1，和ν3基本。部分分配也提出了各种组合波段的NH3。对NH3和ND 3的ν2带的详细分析表明，这两种同位素异构体几乎都是自由转子;振动能蓝移1-2%;旋转常数和反转隧道分裂分别为气相值的91-94%和67- 75%。对于不能旋转弛豫的较高状态，VIR谱线的形状较窄（0.2-0.4 cm（-1）），而对于可以旋转弛豫的较高状态，VIR谱线的形状较宽（>1 cm（-1））。我们报告并分配了一些NH3诱导的红外吸收特性的pH 2主机附近4150 cm（-1），沿着与合作的过渡，涉及同时振动激发的pH 2分子和旋转反转激发的NH3。NH_3和ND_3在1.8K下的反应均符合一级动力学，速率常数分别为k = 1.88（16）× 10 ~（-3）s（-1）和k = 1.08（8）× 10 ~（-3）s（-1）。将这些测得的速率常数与Ar基质中NH3的先前测量值进行比较，并与在固体pH 2中分离的其它掺杂剂分子的速率常数进行比较。
We present matrix isolation infrared absorption spectra of NH3 and ND3 trapped in solid parahydrogen (pH2) at temperatures around 1.8 K. We used the relatively slow nuclear spin conversion (NSC) of NH3 and ND3 in freshly deposited pH2 samples as a tool to assign the sparse vibration-inversion-rotation (VIR) spectra of NH3 in the regions of the ν2, ν4, 2ν4, ν1, and ν3 bands and ND3 in the regions of the ν2, ν4, ν1, and ν3 fundamentals. Partial assignments are also presented for various combination bands of NH3. Detailed analysis of the ν2 bands of NH3 and ND3 indicates that both isotopomers are nearly free rotors; that the vibrational energy is blue-shifted by 1-2%; and that the rotational constants and inversion tunneling splitting are 91-94% and 67-75%, respectively, of the gas-phase values. The line shapes of the VIR absorptions are narrow (0.2-0.4 cm(-1)) for upper states that cannot rotationally relax and broad (>1 cm(-1)) for upper states that can rotationally relax. We report and assign a number of NH3-induced infrared absorption features of the pH2 host near 4150 cm(-1), along with a cooperative transition that involves simultaneous vibrational excitation of a pH2 molecule and rotation-inversion excitation of NH3. The NSCs of NH3 and ND3 were found to follow first-order kinetics with rate constants at 1.8 K of k = 1.88(16) × 10(-3) s(-1) and k = 1.08(8) × 10(-3) s(-1), respectively. These measured rate constants are compared to previous measurements for NH3 in an Ar matrix and with the rate constants measured for other dopant molecules isolated in solid pH2.