Synchrotron and laser-based gas-phase spectroscopy of radicals and other unusual molecules

解锁分子结构和内部物理的根本关键在于理解它们吸收和发射的光的颜色的模式。我们通过用激光或其他光源探测分子来获得这些图案--分子光谱。由于光谱是特定分子的唯一识别符，通过将从这些天体获得的光谱与在地球上获得的光谱进行比较，我们可以确定有关大气或彗星、星云、恒星和星际介质等天体物理对象的组成的重要信息。 在我们新不伦瑞克大学的实验室里，我的学生们对我们在快速移动的分子喷流中创造的含金属分子进行实验，并用指向喷流的直角激光来探测它们。我们还使用激光探测分子，其特征是由一串碳原子组成的主干，这是我们通过使含碳气体经受电放电而产生的。在这两种情况下，感兴趣的分子都是高度活性和不稳定的自由基，只以微量存在，需要非常高灵敏度的技术来研究。这类分子经常出现在天体物理环境中，在那里它们可以与之反应的物质密度非常低。 位于密苏里州萨斯卡通的加拿大光源同步加速器的建造为分子光谱学实验增加了一种令人兴奋的新可能性--获得非常长波长的强光和准直良好的光。同步加速器光使我们能够在电磁光谱中困难的2-30太赫兹范围内快速获得极高质量的光谱，许多具有天体物理意义的较大分子的基本振动都位于该区域。许多目前活跃的星载仪器对这一区域很敏感，我和我的学生收集的数据提供了一个宝贵的数据库，可以与这些卫星从我们周围宇宙收集的光谱进行比较。

A fundamental key to unlocking the structure and the internal physics of molecules lies in understanding patterns in the colours of light that they absorb and emit. We obtain these patterns - the molecular spectrum - by probing the molecules with lasers, or with other light sources. Since the spectrum is a unique identifier for a particular molecule, we can determine important information about the composition of the atmosphere, or of astrophysical objects like comets, nebulae, stars, and the interstellar medium, by comparing spectra obtained from these objects to those obtained on Earth. In our laboratory at the University of New Brunswick, my students experiment on metal-bearing molecules that we create in a fast-moving molecular jet, and probe them with laser beams directed at right angles to the jet. We also use lasers to probe molecules featuring a backbone composed of a string of carbon atoms, which we create by subjecting carbon-bearing gases to electrical discharges. In both cases, the molecules of interest are highly reactive and unstable radicals, present in only trace amounts and requiring techniques of very high sensitivity to study. Such molecules are frequently found in astrophysical environments where the density of material with which they can react is very low. The construction of the Canadian Light Source synchrotron in Saskatoon, SK has added an exciting new possibility for molecular spectroscopy experiments - access to intense and well-collimated light at very long wavelengths. The synchrotron light allows us to rapidly acquire spectra of extremely high quality in the difficult 2-30 terahertz region of the electromagnetic spectrum, where the fundamental vibrations of many larger molecules of astrophysical interest lie. Many currently-active satellite-borne instruments are sensitive to this region, and the data my students and I collect provides a valuable database for comparison with the spectra these satellites collect from the universe around us.