We report a detailed study on the IR spectroscopy of HCl-water complexes in superfluid helium nanodroplets in the frequency range from 2660 to 2675 cm(-1). We have recorded spectra of HCl-H2(16)O as well as of HCl-H2(18)O complexes and compared these results with theoretical predictions. In addition, we have carried out mass-selective intensity measurements as a function of partial pressure of HCl as well as of H2(18)O (pick-up curves). The results support a scenario where the IR-absorption in this part of the spectrum contains contributions from undissociated as well as from dissociated clusters with Cl(-)(H2O)3(H3O)(+) being the smallest dissociated complex. These findings are corroborated by additional electric field measurements yielding the orientation of the vibrational transition moment with respect to the permanent dipole moment. As a result we are able to assign a broad absorption band starting at 2675 cm(-1) to dissociated HCl-water clusters (HCl)1(H2O)n with n ≥ 4. The two narrow absorption lines at 2667.9 cm(-1) and 2670 cm(-1) are assigned to an undissociated cluster, in agreement with previous studies.

We report the infrared spectra of HCl, (HCl)2, and H2O-HCl in liquid helium nanodroplets in the frequency region between 2680 and 2915 cm(-1). For the HCl monomer a line width of 1.0 cm(-1) (H35Cl) corresponding to a lifetime of 5.3 ps was observed. The line broadening indicates fast rotational relaxation similar to that previously observed for HF. For (HCl)2 the free HCl as well as the bound HCl stretching band has been observed. The nu2+ bands of (HCl)2 could be rotationally resolved, and rotational constants were deduced from the spectra. We observed both the allowed and the symmetry forbidden transition. However, the forbidden "broken symmetry" tunneling transition of the mixed dimer shows an intensity that is considerably enhanced compared to the gas phase. Upon the basis of the present measurements we were able to calculate the tunneling splitting in the excited state. The tunneling splitting is found to be reduced by 28% compared to the gas phase. Transitions from the ground state to the Ka=1 level of the free HCl stretch (nu1) are recorded and show considerable line broadening with a line width of 2 cm(-1). The excited state Ka=1 has an additional rotational energy of about 10 cm(-1), thereby allowing fast rotational relaxation by coupling to helium excitations. In addition we observed the HCl stretch of the HCl-H2O dimer, which exhibits an unusually large width (1.7 cm(-1) for H35Cl)) and large red shift (8.5 cm(-1)), compared to the gas-phase values. The large-amplitude motion originating from the libration mode of the HCl-H2O complex is supposed to act as a fast relaxation manifold.

We present the results of an IR spectroscopic study of pyridine-water heterodimer formation in helium nanodroplets. The experiments were carried out in the frequency range of the pyridine C-H stretch region (3055-3100 cm À1 ) and upon water deuteration in the D-O stretch region (2740-2800 cm À1 ). In order to come to an unambiguous assignment we have determined the angle between the permanent dipole and the vibrational transition moment of the aggregates. The experiments have been accompanied by theoretical simulations which yielded two minimum structures with a 16.28 kJ mol À1 energy difference.The experimentally observed bands were assigned to two structures with different H-bonds: an NÁ Á ÁH bond and a bifurcated OÁ Á ÁH-C bond.

Die Untersuchung der Gründe für den Studienabbruch von Studierenden in MINT-Fächern ist wegen des akuten Fachkräftemangels von großer Bedeutung. Dabei ist bisher wenig über Unterschiede zwischen MINT-Studiengängen, aber auch im Vergleich zu anderen Studiengängen, hinsichtlich der Abbruchgründe bekannt. Die längsschnittlich angelegte Studie untersucht daher individuelle Einflussfaktoren auf den Studienerfolg und Studienabbruch in zwei typischen MINT-Studiengängen (Chemie und Maschinenbau) und kontrastierend dazu in Studiengängen aus dem sozialwissenschaftlichen Bereich (Politikwissenschaft, Soziologie, Soziale Arbeit). Während in bisherigen Studien (z.B. Heublein et al., 2017) fachübergreifende Prädiktoren für den Studienabbruch identifiziert werden konnten, wurde in den Analysen dieser Studie festgestellt, dass sich diese zwischen den Fächern und auch zwischen unterschiedlichen Hochschultypen sehr unterschiedlich auswirken. Vor allem die Sozialwissenschaften zeigen im Vergleich zu den MINT-Fächern einen deutlich geringeren Einfluss des Fachwissens auf den Studienabbruch.