@article{PremkeWirthsPentlehneretal.2014, author = {Premke, Tobias and Wirths, Eva-Maria and Pentlehner, Dominik and Riechers, Ricarda and Lehnig, Rudolf and Vdovin, Alexander and Slenczka, Alkwin}, title = {Microsolvation of molecules in superfluid helium nanodroplets revealed by means of electronic spectroscopy}, series = {Frontiers in Chemistry}, volume = {2014}, journal = {Frontiers in Chemistry}, number = {2}, year = {2014}, abstract = {The empirical model explaining microsolvation of molecules in superfluid helium droplets proposes a non-superfluid helium solvation layer enclosing the dopant molecule. This model warrants an empirical explanation of any helium induced substructure resolved for electronic transitions of molecules in helium droplets. Despite a wealth of such experimental data, quantitative modeling of spectra is still in its infancy. The theoretical treatment of such many-particle systems dissolved into a quantum fluid is a challenge. Moreover, the success of theoretical activities relies also on the accuracy and self-critical communication of experimental data. This will be elucidated by a critical resume of our own experimental work done within the last ten years. We come to the conclusion that spectroscopic data and among others in particular the spectral resolution depend strongly on experimental conditions. Moreover, despite the fact that none of the helium induced fine structure speaks against the empirical model for solvation in helium droplets, in many cases an unequivocal assignment of the spectroscopic details is not possible. This ambiguity needs to be considered and a careful and critical communication of experimental results is essential in order to promote success in quantitatively understanding microsolvation in superfluid helium nanodroplets.}, language = {en} } @article{RiechersPentlehnerSlenczka2013, author = {Riechers, Rudolf and Pentlehner, Dominik and Slenczka, Alkwin}, title = {Microsolvation in superfluid helium droplets studied by the electronic spectra of six porphyrin derivatives and one chlorine compound}, series = {The Journal of Chemical Physics}, journal = {The Journal of Chemical Physics}, number = {138}, year = {2013}, abstract = {After almost two decades of high resolution molecular spectroscopy in superfluid helium droplets, the understanding of microsolvation is still the subject of intense experimental and theoretical research. According to the published spectroscopic work including microwave, infrared, and electronic spectroscopy, the latter appears to be particularly promising to study microsolvation because of the appearance of pure molecular transitions and spectrally separated phonon wings. Instead of studying the very details of the influence of the helium environment for one particular dopant molecule as previously done for phthalocyanine, the present study compares electronic spectra of a series of non-polar porphyrin derivatives when doped into helium droplets consisting of 104-105 helium atoms. Thereby, we focus on the helium-induced fine structure, as revealed most clearly at the corresponding electronic origin. The interpretation and the assignment of particular features obtained in the fluorescence excitation spectra are based on additional investigations of dispersed emission spectra and of the saturation behavior. Besides many dopant-specific results, the experimental study provides strong evidence for a particular triple peak feature representing the characteristic signature of helium solvation for all seven related dopant species.}, language = {en} }