@inproceedings{WoerthmannLindnerBriesen2021, author = {W{\"o}rthmann, Mario and Lindner, Johannes A. and Briesen, Heiko}, title = {Gezieltes Einstellen der Schutzwirkung homogener Schmelzcoatings}, series = {Jahrestreffen der ProcessNet-Fachgruppen Lebensmittelverfahrenstechnik, Mischvorg{\"a}nge und Grenzfl{\"a}chenbestimmte Systeme und Prozesse 2021}, booktitle = {Jahrestreffen der ProcessNet-Fachgruppen Lebensmittelverfahrenstechnik, Mischvorg{\"a}nge und Grenzfl{\"a}chenbestimmte Systeme und Prozesse 2021}, editor = {Dechema,}, year = {2021}, language = {en} } @article{StromeckFaderlPentlehnerKensyetal.2011, author = {Stromeck-Faderl, A. and Pentlehner, Dominik and Kensy, U. and Dick, B.}, title = {High-resolution electronic spectroscopy of the BODIPY chromophore in supersonic beam and superfluid helium droplets}, series = {CHEM-PHYS-CHEM, Special Issue: Laser Chemistry and Spectroscopy}, journal = {CHEM-PHYS-CHEM, Special Issue: Laser Chemistry and Spectroscopy}, number = {12}, year = {2011}, abstract = {We present the fluorescence excitation and dispersed emission spectra of the parent compound of the boron dipyrromethene (BODIPY) dye class measured in a supersonic beam and isolated in superfluid helium nanodroplets. The gas-phase spectrum of the isolated molecules displays many low-frequency transitions that are assigned to a symmetry-breaking mode with a strongly nonharmonic potential, presumably the out-of-plane wagging mode of the BF2 group. The data are in good agreement with transition energies and Franck-Condon factors calculated for a double minimum potential in the upper electronic state. The corresponding transitions do not appear in the helium droplet. This is explained with the quasi-rigid first layer of helium atoms attached to the dopant molecule by van der Waals forces. The spectral characteristics are those of a cyanine dye rather than that of an aromatic chromophore.}, language = {en} } @article{SlenczkaPentlehner2013, author = {Slenczka, Alkwin and Pentlehner, Dominik}, title = {Electronic spectroscopy of 9,10-dichloroanthracene inside helium droplets}, series = {The Journal of Chemical Physics}, journal = {The Journal of Chemical Physics}, number = {138}, year = {2013}, abstract = {The spectroscopy of molecules doped into superfluid helium droplets provides information on both, the dopant molecule and the helium environment. Electronic spectra of 9,10-dichloroanthracene in helium droplets are presented and compared with corresponding gas phase spectra to unravel the influence of the helium environment. The combined investigation of fluorescence excitation and dispersed emission provides information on dynamic processes in addition to energetic conditions. For vibronic states, the helium induced decay channels dominate over all intramolecular channels that contribute to the gas phase behavior. In addition to the triplet splitting caused by the Cl isotopes, a fine structure resolved for all transitions in the fluorescence excitation spectrum was found, which is the signature of microsolvation of this compound in helium droplets. This fine structure is identified as a single pure molecular transition accompanied by a sharply structured phonon wing. The corresponding fine structure measured for bare anthracene shows remarkable differences.}, language = {en} } @inproceedings{SchwarzLindner2023, author = {Schwarz, Benedikt and Lindner, Johannes A.}, title = {Automatisierte Prozessoptimierung durch einen adaptiven, dynamischen Mischer}, series = {Jahrestreffen der DECHEMA-Fachgruppen Extraktion und Mischvorg{\"a}nge}, booktitle = {Jahrestreffen der DECHEMA-Fachgruppen Extraktion und Mischvorg{\"a}nge}, editor = {Dechema,}, year = {2023}, 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} } @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{PentlehnerSlenczka2015, author = {Pentlehner, Dominik and Slenczka, Alkwin}, title = {Helium induced fine structure in the electronic spectra of anthracene derivatives doped into superfluid helium nanodroplets}, series = {The Journal of Chemical Physics}, journal = {The Journal of Chemical Physics}, number = {142}, year = {2015}, abstract = {Electronic spectra of organic molecules doped into superfluid helium nanodroplets show characteristic features induced by the helium environment. Besides a solvent induced shift of the electronic transition frequency, in many cases, a spectral fine structure can be resolved for electronic and vibronic transitions which goes beyond the expected feature of a zero phonon line accompanied by a phonon wing as known from matrix isolation spectroscopy. The spectral shape of the zero phonon line and the helium induced phonon wing depends strongly on the dopant species. Phonon wings, for example, are reported ranging from single or multiple sharp transitions to broad (Δν > 100 cm-1) diffuse signals. Despite the large number of example spectra in the literature, a quantitative understanding of the helium induced fine structure of the zero phonon line and the phonon wing is missing. Our approach is a systematic investigation of related molecular compounds, which may help to shed light on this key feature of microsolvation in superfluid helium droplets. This paper is part of a comparative study of the helium induced fine structure observed in electronic spectra of anthracene derivatives with particular emphasis on a spectrally sharp multiplet splitting at the electronic origin. In addition to previously discussed species, 9-cyanoanthracene and 9-chloroanthracene will be presented in this study for the first time.}, language = {en} } @article{PentlehnerSlenczka2012, author = {Pentlehner, Dominik and Slenczka, Alkwin}, title = {Microsolvation of anthracene inside superfluid helium nanodroplets}, series = {Journal of Molecular Physics, Special Issue: Dudley Herschbach Festschrift}, journal = {Journal of Molecular Physics, Special Issue: Dudley Herschbach Festschrift}, number = {110}, year = {2012}, abstract = {This article reports on the microsolvation of anthracene in superfluid helium nanodroplets as revealed by electronic spectroscopy. Among the polyacene molecules benzene, naphthalene, anthracene, tetracene and pentacene only anthracene and tetracene have been found to exhibit multiplet splitting of the electronic and vibronic transitions which can not be explained by a rotational fine structure. The experimental approach for the investigation of the multiplet is the combined investigation of the fluorescence excitation spectrum and dispersed emission spectra. New experimental data are presented on the microsolvation of anthracene in helium droplets. A detailed analysis of the anthracene data will be contrasted to corresponding data on tetracene. These data together with those reported for benzene, naphthalene and pentacene might serve to test and develop theoretical models which are needed to understand microsolvation of single molecules in superfluid helium droplets.}, language = {en} } @article{PentlehnerRiechersDicketal.2009, author = {Pentlehner, Dominik and Riechers, Ricarda and Dick, B. and Slenczka, Alkwin and Even, U. and Lavie, N. and Brown, R. and Luria, K.}, title = {Rapidly pulsed helium droplet source}, series = {Review of scientific instruments}, journal = {Review of scientific instruments}, number = {80}, year = {2009}, abstract = {A pulsed valve connected to a closed-cycle cryostat was optimized for producing helium droplets. The pulsed droplet beam appeared with a bimodal size distribution. The leading part of the pulse consists of droplets suitable for doping with molecules. The average size of this part can be varied between 104 and 106 helium atoms, and the width of the distribution is smaller as compared to a continuous-flow droplet source. The system has been tested in a single pulse mode and at repetition rates of up to 500 Hz with almost constant intensity. The droplet density was found to be increased by more than an order of magnitude as compared to a continuous-flow droplet source.}, language = {en} } @article{PentlehnerRiechersVdovinetal.2011, author = {Pentlehner, Dominik and Riechers, R. and Vdovin, A. and P{\"o}tzl, G.M. and Slenczka, A.}, title = {Electronic spectroscopy of molecules in superfluid helium nanodroplets: an excellent sensor for intramolecular charge redistribution}, series = {The Journal of Physical Chemistry, Special Issue: J. Peter Toennies Festschrift}, journal = {The Journal of Physical Chemistry, Special Issue: J. Peter Toennies Festschrift}, number = {115}, year = {2011}, abstract = {Electronic spectra of molecules doped into superfluid 4He nanodroplets reveal important details of the microsolvation in superfluid helium. The vibrational fine structure in the electronic spectra of phthalocyanine derivatives and pyrromethene dye molecules doped into superfluid helium droplets have been investigated. Together with previous studies on anthracene derivatives [J. Chem. Phys.2010, 133, 114505] and 3-hydroxyflavone [J. Chem. Phys.2009, 131, 194307], the line shapes vary between two limiting cases, namely, sharp Lorentzians and nonresolved vibrational fine structure. All different spectral signatures are initiated by the same effect, namely, the change of the electron density distribution initiated by the electronic excitation. This change can be quantified by the difference of the electrostatic moments of the molecule in the electronic ground state and the corresponding Franck-Condon point in the excited state. According to the experimental data, electronic spectroscopy suffers from drastic line broadening when accompanied by significant changes of the charge distribution, in particular, changes of the dipole moment. Vice versa, the vibrational fine structure in electronic spectra of molecules doped into helium droplets is highly sensitive to changes of the electron density distribution.}, language = {en} }