Mid-Infrared Spectroscopy of the Interstellar Medium

Lacy博士已经构建了一个梯级光谱仪，它比其他可用的仪器在中红外波长的中等到高分辨率的光谱更敏感。有了这笔资金，他将继续在光谱的这个波长区域进行开创性的工作。他将重点研究三个项目：1)他将通过观察气态和固相中各种分子的吸收来研究气相和颗粒表面反应对分子云组成的相对重要性；2)他将研究分子氢的纯旋转线发射，了解激波气体和光解区域的条件，并确定氢与一氧化碳的比例；3)观察氖离子和硫离子的中红外发射谱线，研究红外发光星系的运动学和激发。对于天文光谱学来说，中红外光谱区有两个主要优势：相对于较短波长的星际消光较小，以及存在一些有趣的光谱特征，特别是分子的振动跃迁和离子的精细结构线。由于消光，许多在可见光或近红外波段无法观测到的物体在中红外波段就可以观测到。分子和离子的光谱线提供了有关新发现物体的运动学和物理条件的宝贵信息。莱西博士的摄谱仪代表了探测中红外波长物体的仪器质量的重大进步。

Dr. Lacy has constructed an echelle spectrograph which is an order of magnitude more sensitive than other available instruments for spectroscopy of moderate to high resolution at mid-infrared wavelengths. With this grant he will continue his pioneering work in this wavelength region of the spectrum. Three projects will be emphasized: 1) He will investigate the relative importance of gas- phase and grain-surface reactions on the composition of molecular clouds by observing absorption of various molecules in the gaseous and solid phases; 2) He will study the pure rotational line emission of molecular hydrogen, to learn about the conditions in shocked gas and photodissociation regions, and to determine the ratio of hydrogen to carbon monoxide; and 3) He will observe the mid-infrared emission lines of ions of neon and sulfur to study the kinematics and excitation of infrared luminous galaxies. There are two principal advantages to the mid-infrared spectral region for astronomical spectroscopy: the small interstellar extinction relative to that at shorter wavelengths, and the presence of several interesting spectral features, notably vibrational transitions of molecules and fine-structure lines of ions. Many objects which are unobservable, because of extinction, at visible or near-infrared wavelengths become accessible in the mid-infrared. Spectral lines of molecules and ions provide valuable information about the kinematics and physical conditions of the newly revealed objects. Dr. Lacy's spectrograph represents a significant advance in the quality of instrumentation for exploring objects at mid-infrared wavelengths.