Oli Ehrler - Academia.edu (original) (raw)

Papers by Oli Ehrler

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Journal of Chemical Physics, Aug 8, 2002

Title: Electronic photodissociation spectroscopy of isolated IrX 6 2-(X=Cl,Br). Authors: Friedric... more Title: Electronic photodissociation spectroscopy of isolated IrX 6 2-(X=Cl,Br). Authors: Friedrich, Jochen; Gilb, Stefan; Ehrler, Oli T.; Behrendt, Anja; Kappes, Manfred M. Affiliation: AA(Institut fur Physikalische Chemie, Universitat ...

KIT Scientific Publishing eBooks, Dec 14, 2006

Dank iii porisation) bzw. einer gepulsten Bogenentladungs-Ionenquelle (PACIS, pulsed arc cluster ... more Dank iii porisation) bzw. einer gepulsten Bogenentladungs-Ionenquelle (PACIS, pulsed arc cluster ion source). Damit gelangen eine Reihe von Untersuchungen an den atomaren Clusteranionen Au-3/6 [17, 18], C-3 , [19], Pt-3 [20], Pd-3/4/7 [21, 22] und Ni-3 [23]. Ziel dieser Arbeit war es, ein Anregungs/Abfrage-Photoelektronenspektroskopie Experiment zur massenselektiven Untersuchung großer, auch in kondensierter Phase darstellbarer molekularer Anionen unter isolierten Bedingungen zu entwickeln, zu charakterisieren und damit erste Messungen durchzuführen. Dazu wurde eine hochintensive Elektrospray-Ionenquelle aufgebaut, die durch den Einsatz einer Radiofrequenz-Ionenführung in der Lage ist, ausreichende Ionenströme zum Einsatz in der Kurzzeit-Spektroskopie aufzubringen. Die kontinuierlich arbeitende Ionenquelle wurde durch die Verwendung einer Ionenfalle an das gepulst betriebene Flugzeit-Massenspektrometer adaptiert, welches in ein Flugzeit-Photoelektronenspektrometer mündet. Durch den Einsatz einer sog. " magnetischen Flasche" wird die vollständige Transmission der Elektronen durch das Spektrometer gewährleistet, so dass in Kombination mit der hohen experimentellen Wiederholrate von ∼ 1 kHz erstmals die Pump/Probe-Spektroskopie an großen isolierten Molekülionen möglich wird. Als Anregungs-und Abfrage-Lasersystem kommt das kommerzielle Kurzpuls-Lasersystem Clark-MXR CPA 2001 zum Einsatz, das durch Verwendung verschiedener Frequenzkonversions-Schemata, sowie durch den Einsatz eines nichtkollinear gepumpten optisch-parametrischen Verstärkers (NOPA) eine Vielzahl von Wellenlängen im sichtbaren und nahen UV-Spektralbereich zur Verfügung stellt. Die ersten Untersuchungen am Fullerenanion C-60 , sowie an multianionischen Phthalocyanin-Derivaten mit verschiedenen Metall-Zentren werden im Folgenden vorgestellt.

Journal of Chemical Physics, Apr 14, 2006

A tandem time-of-flight mass spectrometer with an intermediate surface was used to quantify elect... more A tandem time-of-flight mass spectrometer with an intermediate surface was used to quantify electron transfer during glancing incidence scattering of hyperthermal C60+ (Ecoll=250–500eV, θin=75°) from (i) self-assembled monolayers of n-alkylthiols on gold (of various chain lengths), (ii) partly fluorinated alkylthiols on gold, as well as (iii) clean gold surfaces. Self-assembled monolayers (SAMs) behave as insulating layers with their thicknesses determining the electron tunneling probability during collision. Correspondingly, a roughly exponential dependence of the neutralization probability on the chain length n was found. A pronounced dependence of the neutral yield on the primary beam kinetic energy indicates that dynamic SAM deformation and associated projectile penetration depth also play a role in determining electron transfer efficiency. Results are consistent with the molecular deformability of SAMs as determined with other experimental methods.

Journal of Physical Chemistry C, Jun 15, 2012

We have synthesized a series of compounds comprising the halide-free cadmium chalcogenide cluster... more We have synthesized a series of compounds comprising the halide-free cadmium chalcogenide cluster dianions [Cd 8 Se(SePh) 16 ] 2− , [Cd 17 Se 4 (SePh) 28 ] 2− , [Cd 17 S 4 (SPh) 28 ] 2− , and [Cd 17 Se 4 (SPh) 28 ] 2− to study their size-and composition-dependent electronic properties free of matrix effects. Toward this end, photoelectron spectra of the isolated dianions electrosprayed from solution were recorded at several detachment photon energies. Together with quantum chemical calculations, these data reveal a systematic correlation between electronic properties such as electron affinities or repulsive Coulomb barriers and the composition/size of these semiconducting cluster complexes. We infer that the excess negative charges are localized at the apical sites of these near-tetrahedral molecules.

Journal of Chemical Physics, Mar 1, 2005

We report laser photoelectron spectra of the doubly negatively charged fullerenes C762−, C782−, a... more We report laser photoelectron spectra of the doubly negatively charged fullerenes C762−, C782−, and C842− at 2.33, 3.49, and 4.66 eV photon energy. From these spectra, second electron affinities and vertical detachment energies, as well as estimates for the repulsive Coulomb barriers are obtained. These results are discussed in the context of electrostatic models. They reveal that fullerenes are similar to conducting spheres, with electronic properties scaling with their size. The experimental spectra are compared with the accessible excited states of the respective singly charged product ions calculated in the framework of time dependent density functional theory.

Journal of Chemical Physics, Aug 21, 2006

We have measured pump/probe photoelectron spectra of mass-selected, near room temperature C60− in... more We have measured pump/probe photoelectron spectra of mass-selected, near room temperature C60− in the gas phase. The lifetime of the vibrationally excited B̃−(Eg2) state at a calculated energy of 1.26eV was found to be τ=2.2±0.2ps. The dominant decay process corresponds to intramolecular radiationless transitions into ground state C60−. This is in contrast to C60 for which pumping at the absorption onset (1.95eV) leads to predominantly intersystem crossing.

Journal of the American Chemical Society, May 1, 2012

Fractionation according to ion mobility and mass-to-charge ratio has been used to select individu... more Fractionation according to ion mobility and mass-to-charge ratio has been used to select individual isomers of deprotonated DNA oligonucleotide multianions for subsequent isomer-resolved photoelectron spectroscopy (PES) in the gas phase. Isomer-resolved PE spectra have been recorded for tetranucleotides, pentanucleotides, and hexanucleotides. These were studied primarily in their highest accessible negative charge states (3−, 4−, and 5−, respectively), as provided by electrospraying from room temperature solutions. In particular, the PE spectra obtained for pentanucleotide tetraanions show evidence for two coexisting classes of gas-phase isomeric structures. We suggest that these two classes comprise: (i) species with excess electrons localized exclusively at deprotonated phosphate backbone sites and (ii) species with at least one deprotonated base (in addition to several deprotonated phosphates). By permuting the sequence of bases in various [A 5−x T x ] 4− and [GT 4 ] 4− pentanucleotides, we have established that the second type of isomer is most likely to occur if the deprotonated base is located at the first or last position in the sequence. We have used a combination of molecular mechanics and semiempirical calculations together with a simple electrostatic model to explore the photodetachment mechanism underlying our photoelectron spectra. Comparison of predicted to measured photoelectron spectra suggests that a significant fraction of the detected electrons originates from the DNA bases (both deprotonated and neutral).

Physical Review Letters, Sep 12, 2003

We report the laser photoelectron spectra of doubly negatively charged C 84 (D 2 and D 2d) using ... more We report the laser photoelectron spectra of doubly negatively charged C 84 (D 2 and D 2d) using 532 nm and 355 nm radiation. From these spectra, values for the second electron affinity and vertical detachment energy, as well as upper and lower limits for the repulsive Coulomb barrier, are obtained. These values are discussed in the context of classical electrostatic models. The experimental spectra are compared with the accessible excited states of the C ÿ 84 product ion calculated in the framework of time dependent density functional theory.

Physical Chemistry Chemical Physics, 2011

Journal of the American Chemical Society, Oct 31, 2008

We present the first photoelectron (PE) spectra of polypeptide polyanions. Combining PE spectrosc... more We present the first photoelectron (PE) spectra of polypeptide polyanions. Combining PE spectroscopy and mass spectrometry provides a direct measurement of the stability of the polyanions with respect to electron detachment and of the repulsive energy between excess charges. The second electron affinity of gramicidin was found to amount to 2.35 (0.15 eV, and the value of the repulsive Coulomb barrier was estimated to be 0.5 (0.15 eV. The spectra are interpreted as resulting from a competition between delayed and direct emission.

Journal of Physical Chemistry A, Jan 18, 2003

Electron autodetachment from isolated metal phthalocyanine-tetrasulfonate tetraanions (MPc(SO 3) ... more Electron autodetachment from isolated metal phthalocyanine-tetrasulfonate tetraanions (MPc(SO 3) 4 4-) (M)Ni, Cu) was studied at room temperature in an FT-ICR mass spectrometer under UHV conditions. For M) Cu, the electron loss rate was measured for the as-prepared isomer mixture. In the case of M) Ni, two chromatographically purified fractions containing different compositions of constitutional isomers were studied. The observed rate constants for these fractions differed by a factor of 37 (5. Photoelectron spectroscopy indicates that both Cu and Ni compounds comprise isomer ensembles which are electronically metastable. Model calculations suggest that the differing electron loss rates observed for the Ni isomer fractions reflect tunneling through repulsive Coulomb barrier surfaces, which are themselves strongly isomer dependent in shape and height.

Journal of the American Chemical Society, 2008

The Journal of Chemical Physics, 2009

The Journal of Physical Chemistry B, 2009

Solvated electrons, and hydrated electrons in particular, are important spe-cies in condensed pha... more Solvated electrons, and hydrated electrons in particular, are important spe-cies in condensed phase chemistry, physics, and biology. Many studies have examined the formation mechanism, reactivity, spectroscopy, and dynamics of electrons in aqueous solution and other solvents, leading to a fundamental understanding of the electron-solvent interaction. However, key aspects of sol-vated electrons remain controversial, and the interaction between hydrated elec-trons and water is of central interest. For example, although researchers generally accept that hydrated electrons, eaq-, occupy solvent cavities, another pic-ture suggests that the electron resides in a diffuse orbital localized on a H3O radical. In addition, researchers have proposed two physically distinct models for the relaxation mechanism when the electron is excited. These models, for-mulated to interpret condensed phase experiments, have markedly different time scales for the internal conversion from the excited p state to...

Excited state dynamics of acetonitrile cluster anions, ðCH3CNÞ n , were investigated using time-r... more Excited state dynamics of acetonitrile cluster anions, ðCH3CNÞ n , were investigated using time-resolved photoelectron imaging (TRPEI) for 20 6 n 6 50. The clusters were excited and then photodetached with femtosecond pump and probe pulses at 790 and 395 nm, respectively. Excited state lifetimes varied between 200 and 270 fs over this size range, showing no obvious size trend. Experimental evidence indicates that we are exciting ‘isomer II’ clusters in which the excess electron is valence-bound to a solvated anionic dimer core. The absence of an obvious size-dependence in the excited state lifetimes is consistent with such a structure. 2009 Elsevier B.V. All rights reserved.