Millimeter-wave spectroscopy and computational chemical studies of biologically significance and interstellar molecules

Abstract

Microwave spectroscopy is a useful technique for the investigation of rotational spectra of gaseous species. And it is one of the most accurate techniques in determining the molecular structures. For the purpose of this project, the first Millimeter-wave (75-110 GHz) Spectrometer in NUS was built. The spectrometer was carefully tested, and a data acquisition system (DAQ) was designed for it. Millimeter-wave spectra of a series of biologically significant and interstellar molecules -- diethyl ether, propylene oxide, pyridine, aniline and 2-aminipyridine were measured. Combined spectral and computational studies on these molecules have been carried out. Studies of diethyl ether gave the accurate spectroscopic parameters of the trans-trans isomer which can be used in the detection of interstellar diethyl ether. The accurate spectra of the propylene oxide (a pre-biotic chiral molecule) can be readily used by the astronomers in the detection of propylene oxide. Assisted by the theoretical computation, 5 vibrational excited states of pyridine have been determined and assigned. The spectral studies of the inversion of the amino group a??NH2 in aniline and 2-aminopyridine were carried out. The differences in the two hydrogen atoms of the amino group in 2-aminopyridine were studied via the spectral analysis of the main species and the deuterated ones of 2-aminopyridine. All these studies would provide useful data for both interstellar detection and the rotational spectral studies of more complicated systems where these molecules are involved.