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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Single Photon Infrared Emission Spectroscopy: A Study of IR Emission from UV Laser Excited PAHs between 3 and 15 μm
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Single Photon Infrared Emission Spectroscopy: A Study of IR Emission from UV Laser Excited PAHs between 3 and 15 μm

机译：单光子红外发射光谱：紫外激光激发的PAH在3至15μm之间的红外发射研究

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Single-photon infrared emission spectroscopy (SPIRES) has been used to measure emission spectra from polycyclic aromatic hydrocarbons (PAHs). A supersonic free-jet expansion has been used to provide emission spectra of rotationally cold and vibrationally excited naphthalene and benzene. Under these conditions, the observed width of the 3.3-μm (C-H stretch) band resembles the bandwidths observed in experiments in which emission is observed from naphthalene with higher rotational energy. To obtain complete coverage of IR wavelengths relevant to the unidentified infrared bands (UIRs), UV laser-induced desorption was used to generate gas-phase highly excited PAHs, Lorentzian band shapes were convoluted with the monochromator-slit function in order to determine the widths of PAH emission bands under astrophysically relevant conditions. Bandwidths were also extracted from bands consisting of multiple normal modes blended together. These parameters are grouped according to the functional groups mostly involved in the vibration, and mean bandwidths are obtained. These bandwidths are larger than the widths of the corresponding UIR bands. However, when the comparison is limited to the largest PAHs studied, the bandwidths are slightly smaller than the corresponding UIR bands. These parameters can be used to model emission spectra from PAH cations and cations of larger PAHs, which are better candidate carriers of the UIRs.
机译：单光子红外发射光谱（SPIRES）已用于测量多环芳烃（PAH）的发射光谱。超音速自由射流膨胀已用于提供旋转冷和振动激发的萘和苯的发射光谱。在这些条件下，观察到的3.3μm（C-H拉伸）带的宽度类似于在实验中观察到的带宽，在该实验中，观察到具有更高旋转能量的萘的发射。为了获得与未识别的红外波段（UIR）相关的IR波长的完整覆盖，使用UV激光诱导的解吸生成气相高度激发的PAHs，用单色仪-狭缝函数对Lorentzian谱带形状进行卷积以确定宽度天体相关条件下PAH发射带的变化还从由多个混合在一起的正常模式组成的频带中提取带宽。根据主要涉及振动的功能组对这些参数进行分组，并获得平均带宽。这些带宽大于相应的UIR频段的宽度。但是，当比较仅限于研究的最大PAH时，带宽略小于相应的UIR频段。这些参数可用于建模来自PAH阳离子和较大PAH的阳离子的发射光谱，PAH阳离子是UIR的更好候选载体。

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