Infrared plus vacuum ultraviolet spectroscopy of neutral and ionic methanol monomers and clusters: New experimental results
Infrared plus vacuum ultraviolet spectroscopy of neutral and ionic methanol monomers and clusters: New experimental results
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DOI：
10.1063/1.2357953
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发表时间：
2006-10-21
影响因子：
4.4
通讯作者：
Bernstein, E. R.
中科院分区：
文献类型：
--
作者：
Hu, Y. J.;Fu, H. B.;Bernstein, E. R.
我们提出了新的观察红外光谱中性甲醇和中性和质子化的甲醇团簇采用红外加真空紫外（vuv）光谱技术。可调谐IR光覆盖2500 - 4500 cm（-1）和5000 - 7500 cm（-1）的能量范围。在超声膨胀冷却甲醇的振动光谱（2500 - 7500 cm（-1））中识别出CH和OH的基本伸缩模、OH泛音模和组合带。本文研究了中性甲醇团簇（CH_3OH）（n）（n = 2，...，..，..，..，..，..，..，..，..，..，..，..，..，..，...，...，...，.............................................................................................................................................................................. 8），证明甲醇二聚体具有自由和键合的OH伸缩特征，而大于二聚体的簇仅显示氢键合的OH伸缩特征。CH伸缩模谱不随团簇尺寸变化。这些结果表明，所有大于二聚体的簇都具有环状结构，其中OH基团参与氢键。CH基团显然不是这种环状结合网络的一部分。质子化甲醇团簇离子（CH_3OH）（n）H + n = 1，…，7中的OH和CH拉伸区域中的尺寸选择的真空紫外加IR光解离光谱进行。自由和氢键OH伸缩的能量随着n的增加呈现蓝移，并且这两个模式在团簇尺寸n = 7时分别收敛到约3670和3400 cm（-1）。(c)2006年，美国物理学会。
We present new observations of the infrared (IR) spectrum of neutral methanol and neutral and protonated methanol clusters employing IR plus vacuum ultraviolet (vuv) spectroscopic techniques. The tunable IR light covers the energy ranges of 2500-4500 cm(-1) and 5000-7500 cm(-1). The CH and OH fundamental stretch modes, the OH overtone mode, and combination bands are identified in the vibrational spectrum of supersonic expansion cooled methanol (2500-7500 cm(-1)). Cluster size selected IR plus vuv nonresonant infrared ion-dip infrared spectra of neutral methanol clusters, (CH3OH)(n) (n=2,...,8), demonstrate that the methanol dimer has free and bonded OH stretch features, while clusters larger than the dimer display only hydrogen bonded OH stretch features. CH stretch mode spectra do not change with cluster size. These results suggest that all clusters larger than the dimer have a cyclic structure with OH groups involved in hydrogen bonding. CH groups are apparently not part of this cyclic binding network. Studies of protonated methanol cluster ions (CH3OH)(n)H+ n=1,...,7 are performed by size selected vuv plus IR photodissociation spectroscopy in the OH and CH stretch regions. Energies of the free and hydrogen bonded OH stretches exhibit blueshifts with increasing n, and these two modes converge to approximately 3670 and 3400 cm(-1) at cluster size n=7, respectively. (c) 2006 American Institute of Physics.