Doctoral Degree: University of Kaiserslautern, Germany, 1998
Postdoctoral Associate: Yale University, New Haven, CT (1999-2001)
Habilitation, Venia Legendi for Physical Chemistry: University of Karlsruhe, Germany, 2005
Awards- Dissertation Award 1999 of the Freundeskreis der Universität Kaiserslautern- Wolfgang-Paul-Award 1999 of the Deutsche Gesellschaft für Massenspektrometrie (German Society for Mass Spectrometry DGMS).- Emmy-Noether-Award of the Deutsche Forschungsgemeinschaft (German Science Foundation), 2002 - 2005- NSF CAREER Award 2009
Gas phase spectroscopy of mass selected ions
Much of the behavior of important species (such as molecular ions, especially in higher charge states, but also DNA, proteins, polysaccharides, building blocks of polymers, and nanoparticles) is only known in a condensed phase environment (mostly solution phase), where interaction with the solvent changes some of the properties of those molecules. In order to elucidate the intrinsic properties of these molecules, and – by comparison with condensed phase data – characterize their interplay with their chemical environment (solvent or surfaces), the molecules have to be studied as isolated entities. This can be achieved using mass selected ion beams. Spectroscopy techniques involving ion beams have had a great impact on the detailed understanding of small molecules and clusters. Some of the techniques have also been applied to biomolecules, and to nanoparticles.
The deposition of energy into isolated biomolecules, nanoparticles, or clusters can lead to their fragmentation or (especially for anions) to a change of their charge state. Different from pure mass spectrometric studies, the application of laser spectroscopy affords the deposition of energy in a defined manner by choosing the laser wavelength and the absorbing chromophore. Investigation of fragmentation pathways at different photon energies can lead to new insight into the photophysics and photochemistry of these complex molecules.
Based on these ideas, our group combines mass spectrometry with laser spectroscopy to characterize positively and negatively charged ions and biomolecules.
Energy flow in molecular chains
All chemical reactions are governed by the nuclear dynamics of molecules, in other words, their patterns of vibrational motion, and any predictive theoretical treatment of chemical reactions needs to describe these motions. Therefore, the way in which vibrational energy flows through, and is redistributed in, molecules after excitation has significant impact on the understanding of chemical reaction dynamics, and for the prospect of coherent control of chemical reactions. Moreover, characterizing energy flow through nanoscale systems has become a critical issue as technology utilizing the progressively smaller sizes of electronic devices encounters the destruction limit of energy density. As a consequence, intramolecular vibrational relaxation (IVR) has long been a field of study. Most experiments in this field have dealt with the question how long it takes for energy to drain out of an exited degree of freedom. “Standard models” of IVR have been used with great success in the modeling of IVR in relatively small molecules. The extension of experiments to larger systems, however, remains a challenging and fertile area for experimental investigation. It is at this break in our current understanding where our approach will provide key data for interfacing the behavior of relatively small molecules accessible for fully quantum mechanical calculations with larger molecules.
We follow a new experimental approach to study the flow of energy as it drains out of a certain vibrational mode and arrives at a well defined place in a molecule. In this approach, we use model systems where the binding energy of an electron in a negatively charged molecule is less than the energies for certain vibrational transitions. This way, we can follow the flow of energy in a molecule by monitoring electron loss and analyzing the kinetic energy distribution of these electrons with high-resolution photoelectron spectroscopy.
Supramolecular chemistry and materials at ultrahigh pressures
Supramolecular chemistry, i.e., the study of non-covalent interactions between molecules, shows great promise in many fields, from soft condensed matter to materials chemistry and molecular machines. While many researchers investigate the behavior properties of supramolecular assemblies and explore various synthetic routes to new materials at ambient conditions, supramolecular assemblies at high pressure have been largely unexplored.
Very high pressures (in the range of 104 atmospheres and higher) allow access to very unconventional thermodynamic parameters, and open avenues to radically different chemistry of supramolecular assemblies. This could result not only in the observation of completely new interactions in simple substances, but in the generation of fundamentally different chemical species from “ordinary” subunits. We investigate supramolecular assemblies based on aromatic compounds as a function of pressure, monitoring the changes in their electronic absorption spectra as pressure increases. The information encoded in the electronic spectra will enable us to understand the changes in the electronic structure of supramolecular assemblies and the weakly bonded nanostructures created by non-covalent interactions.
Nucleation and growth kinetics nanoparticles
Nanoparticles have received enormous interest in the past few years, since they promise new and exciting applications in many fields, ranging from sensors to drug delivery. Even so, there is a lack of fundamental understanding regarding the basic mechanisms of nanoparticle nucleation and growth. At the same time, control over the size and shape distribution of nanoparticle synthesis is still elusive in many cases, hampering more advanced application. We aim to gain understanding of nanoparticle growth kinetics using photochemical approaches in concert with Raman spectroscopy techniques.
C. L. Adams, H. Schneider, J. M. Weber
“Vibrational Autodetachment – Intramolecular Vibrational Relaxation Translated Into Electronic Motion“
accepted for publication as an Invited Feature Article to J. Phys. Chem. A, January 2010
J. C. Marcum, A. Halevi, and J. M. Weber
“UV Photodamage to Isolated Mononucleotides Photodissociation Spectra and Fragment Channels”
Phys. Chem. Chem. Phys. 11 (2009) 1740
C. L. Adams, H. Schneider, K. M. Ervin, J. M. Weber
“Low-energy photoelectron imaging spectroscopy of nitromethane anions: Electron affinity, vibrational features, anisotropies, and the dipole-bound state”
J. Chem. Phys. 130 (2009) 074307
H. Schneider, K. Takahashi, R. T. Skodje, J. M. Weber
“Infrared spectra of SF6-·HCOOH·Arn(n = 0 – 2): Infrared-triggered reaction and Ar-induced inhibition”
J. Chem. Phys., 130 (2009) 174302
J. C. Marcum, J. M. Weber
“Electronic photodissociation spectra and decay pathways of gas-phase IrBr62-”
J. Chem. Phys., 131 (2009) 194309
H. Schneider, K. M. Vogelhuber, F. Schinle, J. F. Stanton, J. M. Weber
“Energy flow in hydrocarbon chains: vibrational spectroscopy of nitroalkane chains using Ar predissociation and electron autodetachment”
J. Phys. Chem. A 112 (2008) 7498
A. N. Gloess, H. Schneider, J. M. Weber, and M. M. Kappes
“Electronically excited states and visible region photodissociation spectroscopy of Au_m^+·Ar_n Clusters (m = 7-9): Molecular dimensionality transition?”
J. Chem. Phys. 128 (2008) 114312
H. Schneider, K. M. Vogelhuber, F. Schinle, and J. M. Weber
“Aromatic Molecules in Anion Recognition: Electrostatics versus H-Bonding”
J. Am. Chem. Soc. 129 (2007) 13022
H. Schneider, K. M. Vogelhuber and J. M. Weber
“Infrared spectroscopy of anionic hydrated fluorobenzenes”
J. Chem. Phys. 127 (2007) 114311
H. Schneider, J. M. Weber, (E. M. Myshakin), (K. D. Jordan), (J. Bopp), (T. Herden), (M. A. Johnson)
“Theoretical and infrared spectroscopic investigation of the O2-·benzene and O4-·benzene complexes”
J. Chem. Phys. 127 (2007) 084319