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Abstract

The objective of this thesis is to investigate molecules of astronomical interest with a multi-spectroscopic approach to allow the chemical inventory of interstellar molecules to be better determined. This will also contribute towards a more comprehensive understanding of their formation mechanisms in the Interstellar medium. The major part of this thesis was done utilizing rotational spectroscopy. Analysis of rotational spectra delivers line lists and rotational constants for the molecules studied. Application of these to the observational data sets allows astronomers to search for the molecules in interstellar space. It is a very structure-sensitive technique that is not only conformer-specific but also isotopologue-specific. The different frequency ranges covered by the rotational spectrometers overlap with various radio telescopes. For example, the low-frequency data overlaps with facilities such as the Jansky Very Large Array and the Effelsberg 100m Radio Telescope. The W-band spectrometer overlaps with the Band 3 operating regime (86-114 GHz) of the Atacama Large Millimeter/submillimeter Array. This makes the laboratory data directly applicable to radio astronomy. In addition to rotational spectroscopy, we also utilized IR spectroscopic techniques like Infrared reflection absorption spectroscopy and IR-UV ion dip spectroscopy. With the commencement of the James Webb Space Telescope, the vibrational spectroscopy data can be used to search the vibrational features of the molecules of interest in the Interstellar medium.