CRASY: Structure determination of neutral molecules and radical

Abstract

Correlated Rotational Alignment Spectroscopy (CRASY) is a powerful spectroscopic technique that can investigate heterogeneous samples and correlate multiple observables in a single experiment. The current mass-CRASY implementation combines rotational spectroscopy and mass spectrometry. We measured the rotational Raman spectra for butadiene in the past. By integrating signals for multiple fragment channels, I achieved an enhanced signal-to-noise (SNR) ratio, which allowed me to assign more rotational transition peaks and determine in more accurate rotational constants. In thesis I also calculate a full molecular structure for butadiene based on the obtained rotational constants. In a CRASY measurement for benzene and perdeuterated benzene, I resolved high resolution rota- tional constants for five benzene isotopologues. The equilibrium structure for benzene was determined based on the experimental data. This result corrected inaccurate benzene structures that had been re- ported in the scientific literature. With this result, I demonstrated that CRASY is highly suitable for the structure determination of non-dipolar molecules. I analyzed two dipolar molecules, furan and thiophene. Rotational constants of furan were fitted in spectra obtained by integrating data for the furan main isotopologue and its fragment channels. Spectra for three rare furan isotopologues (13C-furan, and 18O-furan) were also resolved. I determined a full furan structure based on the obtained rotational constants. High-resolution rotational Raman spectra for thiophene were analyzed. Here, I obtained rotational constants for thiophene and the 34S-thiophene isotopologue. A pyrolysis nozzle for radical-CRASY experiments was designed and constructed. Testing revealed that pyrolysis temeratures up to ∼ 1,000 ◦C can be achieved with the chosen design. Key Word: Multi-dimensional spectroscopy, Rotational spectroscopy, Mass spectroscopy, High-resolution technique, Structure determination, Reactive species.