Experimental and theoretical investigations of molecular ions by spectroscopy as well as ion mobility and mass spectrometry The aim of this thesis was the elucidation of different ionization methods (resonance enhanced multiphoton ionization – REMPI electrospray ionization – ESI atmospheric pressure chemical ionization – APCI) in ion mobility (IM) spectrometry. In order to gain a better understanding of the ionization processes several spectroscopic mass spectrometric and theoretical methods were also used. Another focus was the development of experimental techniques including a high resolution spectrograph and various combinations of IM and mass spectrometry.The novel high resolution 2D spectrograph facilitates spectroscopic resolutions in the range of commercial echelle spectrographs. The lowest full width at half maximum of a peak achieved was 25 pm. The 2D spectrograph is based on the wavelength separation of light by the combination of a prism and a grating in one dimension and an etalon in the second dimension. This instrument was successfully employed for the acquisition of Raman and laser induced breakdown spectra.Different spectroscopic …