Untersuchung der molekularen Aggregate (TCNB)2(TCNB)_{2}, HDO−H2OHDO-H_{2}O und 1,2HCI(H2O)4^{1,2}HCI(H_{2}O)_{4} in Heliumnanotröpfchen

Im Rahmen dieser Arbeit wurden 1,2,4,5-Tetracyanobenzol (TCNB) und $(TCNB)_{2}$, $HDO-H_{2}O$ und $^{1,2}HCl(H_{2}O)_{4}$ mit hochauflösender Infrarotspektroskopie in Heliumnanotröpfchen (0.37 K) untersucht. Dabei wurde gezeigt, dass bei der schrittweisen Anlagerung von $H_{2}O$ an HCl ab dem 4. Molekül $H_{2}O$ ein Solvens-separiertes Ionenpaar $H_{3}O^{+}(H_{2}O)_{3}Cl^{-}$ gebildet wird. Mit Isotopenmessungen, optisch-selektiven Massenspektren, Einlagerungskurven und im Vergleich mit theoretischen Berechnungen konnte der Dissoziationsmechanismus aufgeklärt werden. Wasserdimere wurde im Bereich der O-D Streckschwingung untersucht, es wurde u.a. die Tunnelbewegung in der supraflüssigen Matrix nachgewiesen. Mit Spektren im Bereich von 3054 $cm^{-1}$ wurde die Struktur von $(TCNB)_{2}$ aufgeklärt. Weiterhin wurden basierend auf infrarotspektroskopischen Daten verschiedener partiell deuterierter Ameisensäuredimere Strukturberechnungen durchgeführt, die zeigten, dass sich die Länge der Wasserstoffbrückenbindung mit Deuterierung verändert

VIBRONIC SPECTROSCOPY OF JET-COOLED 1,4-PHENYLENE DIISOCYANIDE

Author Institution: Department of Chemistry, Purdue University, West Lafayette, IN 47907This talk will present results of a gas phase, jet-cooled vibronic spectroscopy study of 1,4-PDI. A fluorescence excitation spectrum spanning the range 35,500-44,100 cm$^{- 1}$ (226.5-281.5 nm) has been recorded, as well as a resonant two photon ionization excitation and UV hole-burning spectrum, in the region of 35,500-36,500 cm$^{-1}$. The S$_0$-S$_1$ origin is a weak band located at 35,566 cm$^{-1}$. The spectrum in the S$_1$ region is dominated by vibronic coupling to the S$_2$ state. Dispersed fluorescence spectra will be presented that uncover and characterize the vibronic coupling. We have also located the S$_0$-S$_2$ origin 5687 cm$^{-1}$ above the S$_0$-S$_1$ origin. Evidence will be presented for the coupling of the S$_2$ levels with nearby S$_1$ levels and for internal conversion from S$_2$ to S$_1$ on the timescale of the fluorescence

SOLVATION OF HCl, AGGREGATION OF H2_2O, HCl AND THEIR DEUTERATED ISOTOPES IN SUPERFLUID He DROPLETS}

this work was supported by FOR 618 of the German Science FoundationAuthor Institution: Department of Physical Chemistry II; Ruhr-University Bochum, Universitatsstr. 150, D-44780We investigate aggregates of HCl, H$_2$O and their deuterated isotopes embedded in superfluid helium using a helium nanodroplet spectrometer combined with a cw infrared OPO set up with an output power of up to 2.7 W and a resolution of better than 0.001 cm$^{-1}$. Depletion spectra of the super cooled aggregates (0.37 K) were recorded between 2650 cm$^{-1}$ and 2720 cm$^{-1}$. We were able to assign the HCl stretch vibration of the HCl-H$_2$O complex. We also observed spectral features of (HCl)$_m$(H$_2$O)$_n$ aggregates and isotopes in the region of the H$_3$O$^+$ stretch vibration. The question of how many H$_2$O molecules are needed to solvate HCl will be addressed

Aggregation-induced dissociation of HCl(H2O)4 below 1 K: the smallest droplet of acid

Acid dissociation and the subsequent solvation of the charged fragments at ultracold temperatures in nanoenvironments, as distinct from ambient bulk water, are relevant to atmospheric and interstellar chemistry but remain poorly understood. Here we report the experimental observation of a nanoscopic aqueous droplet of acid formed within a superfluid helium cluster at 0.37 kelvin. High-resolution mass-selective infrared laser spectroscopy reveals that successive aggregation of the acid HCl with water molecules, HCl(H2O)n, readily results in the formation of hydronium at n = 4. Accompanying ab initio simulations show that undissociated clusters assemble by stepwise water molecule addition in electrostatic steering arrangements up to n = 3. Adding a fourth water molecule to the ringlike undissociated HCl(H2O)3 then spontaneously yields the compact dissociated H3O+(H2O)3Cl– ion pair. This aggregation mechanism bypasses deep local energy minima on the n = 4 potential energy surface and offers a general paradigm for reactivity at ultracold temperatures

Vibronic Spectroscopy of a Nitrile/Isonitrile Isoelectronic Pair: <i>para</i>-Diisocyanobenzene and <i>para</i>-Isocyanobenzonitrile

The ultraviolet spectroscopy of isoelectronic pair <i>para</i>-diisocyanobenzene (<i>p</i>DIB) and <i>para</i>-isocyanobenzonitrile (<i>p</i>IBN) has been studied under gas-phase, jet-cooled conditions. These molecules complete a sequence of mono and disubstituted nitrile/isonitrile benzene derivatives, enabling a comparison of the electronic effects of such substitution. Utilizing laser-induced fluorescence (LIF) and resonant two-photon ionization (R2PI) spectroscopy, the S₀–S₁ electronic origins of <i>p</i>DIB and <i>p</i>IBN have been identified at 35 566 and 35 443 cm^–1, respectively. In <i>p</i>DIB, the S₀–S₁ origin is very weak, with b_3g fundamentals induced by vibronic coupling to the S₂ state dominating the spectrum at 501 cm^–1 (ν₁₇, isocyano bend) and 650 cm^–1 (ν₁₆, ring distortion). The spectrum extends over 5000 cm^–1, remaining sharp and relatively uncongested over much of this range. Dispersed fluorescence (DFL) spectra confirm the dominating role played by vibronic coupling and identify Franck–Condon active ring modes built off the vibronically-induced bands. In <i>p</i>DIB, the S₂ state has been tentatively observed at about 6100 cm^–1 above the S₀–S₁ origin. In <i>p</i>IBN, the S₀–S₁ origin is considerably stronger, but vibronic coupling still plays an important role, involving fundamentals of b₂ symmetry. The bending mode of the nitrile group dominates the vibronically-induced activity. Calculations carried out at the TD-DFT B3LYP/6-31+G­(d) level of theory account for the extremely weak S₀–S₁ oscillator strength of <i>p</i>DIB and the larger intensity of the S₀–S₁ origins of <i>p</i>IBN and <i>p</i>DCB (<i>para</i>-dicyanobenzene) as nitrile groups are substituted for isonitrile groups. In <i>p</i>DIB, a nearly perfect cancellation of transition dipoles occurs due to two one-electron transitions that contribute nearly equally to the S₀–S₁ transition. The spectra of both molecules show no clear evidence of charge-transfer interactions that play such an important role in some cyanobenzene derivatives

Is there a Tornado in Alex's Blood Flow? A Case Study for Narrative Medical Visualization

Narrative visualization advantageously combines storytelling with new media formats and techniques, like interactivity, to create improved learning experiences. In medicine, it has the potential to improve patient understanding of diagnostic procedures and treatment options, promote confidence, reduce anxiety, and support informed decision-making. However, limited scientific research has been conducted regarding the use of narrative visualization in medicine. To explore the value of narrative visualization in this domain, we introduce a data-driven story to inform a broad audience about the usage of measured blood flow data to diagnose and treat cardiovascular diseases. The focus of the story is on blood flow vortices in the aorta, with which imaging technique they are examined, and why they can be dangerous. In an interdisciplinary team, we define the main contents of the story and the resulting design questions. We sketch the iterative design process and implement the story based on two genres. In a between-subject study, we evaluate the suitability and understandability of the story and the influence of different navigation concepts on user experience. Finally, we discuss reusable concepts for further narrative medical visualization projects.publishedVersio