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Zusammenfassung:
Chiral molecules are of considerable interest across various fields of science, particularly due to their pivotal role in pharmaceuticals and biological processes. Over recent decades, spectroscopic techniques for chiral analysis have developed. Among these, the enantiomer- specific state transfer (ESST) method has emerged as a standout approach. Based on microwave (MW) spectroscopy, ESST facilitates chiral separation in different rotational states. Recent advancements of this method incorporate ultraviolet (UV) radiation into ESST to improve the transfer efficiency, which necessitates a precise understanding of the distinct rotational energy level structures in both the ground and the first electronically excited state of the target molecules.
Building on this need, this thesis presents a comprehensive high-resolution UV spectro- scopic study of 1-phenylethanol, a potential target molecule for ESST studies. Using a jet-cooled pulsed molecular beam, we performed vibrationally and rotationally resolved UV spectroscopy through resonance-enhanced multiphoton ionization (REMPI) and laser- induced fluorescence (LIF), respectively. Our work aimed to characterize the rotational energy level structure of 1-phenylethanol in the first electronically excited state.
We recorded a vibrationally resolved REMPI spectra of the S1 ← S0 electronic transition using a pulsed dye laser. Through comparisons with theoretical one-photon absorption calculations, we identified the origin band and additional vibrational features in the spectrum. Additionally, we determined the lifetime of the S1 state to be 70 ns using two time-delayed pulsed lasers, corresponding to a natural linewidth of 2.2 MHz
Subsequently, a rotationally resolved spectrum of the origin band of the S1 ← S0 electronic transition, initially identified using REMPI, was recorded via LIF detection. The linewidth of the spectrum was measured to be 54 MHz, suggesting that Doppler broadening is a significant factor affecting the observed spectral linewidth. The measured spectrum was analyzed using the PGOPHER software. Starting with known and calculated rotational constants, we refined the fit to the measured data to accurately determine the rotational constants of the S1 state. These parameters provide a detailed understanding of the rotational energy level structure, which is essential for potential applications in ESST.
