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。该方法具有获取宽带频谱（1000-4000 MHz）的能力，而不会降低在常规吸收光谱学（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.光谱学测量的压力扩大光谱，讨论其形状和推导压力扩大或移位参数。2.容易分配的过渡的分子表现出复杂的光谱模式，和3。多重或同时量子态观测。本研究所用的实验装置是日本宇宙航空研究开发机构（JAXA）筑波空间中心的超导接收机系统，工作频率为0.6THz。首先，我们成功地测量了氯化氢分子两种同位素在2000 ~ 2000 ℃压力范围内的J=1-0转动跃迁的发射光谱。 ...更多信息 n 0.3 ~ 200 hPa。通过分析所观察到的发射光谱的形状，可以推导出分子对氮和氧的压力展宽和压力位移参数。同样的测量也进行了乙腈分子，这被认为是重要的对流层化学。可靠的压力展宽和位移参数将有助于利用遥感技术从观测的大气光谱中反演分子的丰度。我们还试图探测由乙腈分子和氦的混合物放电获得的等离子体的发射光谱。氰化氢，放电产生的反应产物之一，观察到其振动激发态。我们的方法使得有可能估计分子的振动温度约为410 K。这些信息将有助于分子动力学的研究。这些结果将发表在分子光谱学杂志上。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