Development of Wideband Terahertz Emission Spectroscopy by using heterodyne receiver

本研究的目的是利用外差探测技术发展太赫兹波段的气相发射光谱。该方法具有获得宽带频谱(1000-4000 MHz)的能力，而不降低在常规吸收光谱(100 kHz或更小)中获得的频率精度。为了证明这些优点，我们论证了以下三点：1.压力展宽光谱的光谱测量，以讨论其形状，并推导出压力展宽或位移参数。2.对呈现复杂光谱模式的分子的跃迁进行简单的指认；3.多个或同时的量子态观测。本研究中使用的实验装置是筑波航天中心日本宇宙航空研究开发机构的超导接收系统，工作频率为0.6THz。首先，我们成功地测量了氯化氢分子的两个同位异构体在…之间的压力范围内J=1-0转动跃迁的发射光谱。更多n 0.3至200百帕。通过分析观测到的发射光谱的形状，可以得到该分子相对于氮气和氧气的压力展宽和压移参数。对乙腈分子也进行了同样的测量，这在对流层化学中被认为是重要的。可靠的压力展宽和位移参数将有助于通过遥感技术从观测到的大气光谱中恢复分子的丰度。我们还试图检测通过放出乙腈分子和氦的混合物而获得的等离子体的发射光谱。氰化氢是放电产生的反应产物之一，它的振动激发态被观察到。我们的方法使得估计分子的振动温度约为410K成为可能。这种信息将有助于分子的动力学研究。这些结果将发表在《分子光谱学》杂志上。较少

The purpose of this study is to develop gas-phase emission spectroscopy at terahertz region by using heterodyne detection technique. The method has a capability of taking a wideband frequency spectra (1000-4000 MHz) without degrading frequency accuracy obtained in the conventional absorption spectroscopy (100 kHz or less). We demonstrated the following three points in order to demonstrate these advantages; 1. Spectroscopic measurements of pressure-broadened spectra to discuss its shape and derive pressure broadening or shift parameters. 2. Easy assignments of transitions of the molecule showing a complicated spectral pattern, and 3. Multiple or simultaneous quantum states observation. The experimental setup used in the present study is a superconducting receiver system at JAXA in Tsukuba Space Center operated at 0.6 THzFirst, we have succeeded to measure emission spectra of J=1-0 rotational transition of the two isotopomers of the hydrogen chloride molecule in the pressure range betwee … More n 0.3 to 200 hPa. Pressure broadening and pressure shift parameters against nitrogen and oxygen for the molecule can be derived by analyzing the shape of the observed emission spectra. The same kind of measurements was also conducted for the acetonitrile molecule, which is considered to be important in the tropospheric chemistry. Reliable pressure broadening and shift parameters will contribute to retrieve abundance of the molecule from the observed atmospheric spectra by remote sensing techniqueWe have also tried to detect emission spectra from the plasma obtained by discharging a mixture of the acetonitrile molecule and helium. The hydrogen cyanide, one of the reaction products produced by a discharge, is observed with its vibrational excited state. Our method makes it possible to estimate of the vibrtional temperature of the molecule to be approximately 410 K. This kind of information will contribute to kinetic study of the molecules.These results will be published in the Journal of Molecular Spectroscopy. Less