Rotational Spectroscopy on Propylene Oxide and Styrene Oxide and Development of a Chirped-Pulse Fourier Transform Spectrometer around 105 GHz

Over the last 60 years, the developments and accomplishments in radio astronomy and molecular astrochemistry have gone hand-in-hand with those of high-resolution rotational spectroscopy and high frequency technology. As of today, about 250 molecules have been found in space by their unambiguous characteristic spectral fingerprints. The majority of the already detected interstellar molecules was identified by the comparison of laboratory data fromhigh-resolution spectrometers operating in the microwave, millimeter wave, and sub-millimeter wave region with the observational spectra that were obtained from radio telescopes. Thus, the acquisition of high-resolution laboratory data and the development of efficient spectrometers to record these spectra are mandatory in order to elucidate the stunning phenomena that can be observed in space. One of the main aims of this work was to develop a high-resolution chirped-pulse Fourier transform spectrometer operating in the millimeter wave region that is able to record rotational spectra of molecules of astrophysical relevance. A variety of concepts and techniques of state-of-the-art chirped-pulse spectrometers and superheterodyne receivers such as segmenting, frequency conversion and mixing, and pulse switching were incorporated into the instrument. The developed spectrometer is an automatised high-resolution chirped-pulse Fourier transform spectrometer that operates between 100–112.5 GHz. It employs a powerful millimeter wave radiation source with an output power of up to 1W(30 dBm). The mean noise temperature of the receiver was characterised by a hot-cold measurement to be about 1153 K. Several molecular spectra were recorded in a room-temperature cell and with supersonic jets withmultipass reflection optics. The spectra exhibit reasonable signal-to-noise ratios and a high frequency accuracy. The results demonstrate that the newly built spectrometer iswell suited to study molecules of astrochemical relevance.