Engineering topics

Gerber, Robert B.

Publications and source records attributed to Gerber, Robert B..

4 records

DOE OSTI2019

Controlling internal degrees: general discussion

Temperature is a very important concept in ion spectroscopy and its control has seen tremendous advances in recent years. Cryogenic ion traps are now found in many experiments and serve as thermostats, reaction vessels, clustering sources and spectroscopic sample chambers. The control over internal degrees of freedom provides routes to forming ions that are relevant at cryogenic temperatures such as in the interstellar medium and to control and lock-in conformations. It also provides a condensing environment and allows weakly bound clusters to be formed, which in turn provides new routes to action spectroscopy. This session will discuss the most recent developments in cryogenic spectroscopy and the research it enables and how new theoretical methods allow the prediction of experimental spectra as a function of temperature. The main discussion topics will cover: the best cooling methods; how temperature can be used to form exotic clusters and weakly interacting systems; and the possibilities for probing conformational locking and metastable structures.

Ahmed, Musahid↗

DOE OSTI2019

Pushing resolution in frequency and time: general discussion

One of the most important aspects of spectroscopy in general is resolution: the higher it is, the more information can be attained. At one end, spectral resolution provides geometric and electronic structural information and insights into weak interactions such as hydrogen bonds. At the other end, temporal resolution provides insight into geometric and electronic structural dynamics. The aim of this session is to provide a forum to discuss the state of the art in terms of resolution in general and how recent advances in light sources and ion mass spectroscopy can be used to study unexplored phenomena and interactions. Theoretical developments also have a key role in this area, particularly in relation to time-resolved measurements, since theoretical predictions are of key importance for providing molecular-insight into the observed experimental dynamics. The key discussion points will revolve around how experiment and theory can best combine to achieve the deepest insight, both in terms of structure and dynamics; and how new light sources may open new horizons.

Simons, Jack↗

DOE OSTI2019

Going large(r): General Discussion

With the introduction of new ion sources and advanced mass-spectrometric techniques coupled to spectroscopy, ever larger complexes are being probed. This increase in size is coupled with an increase in complexity requiring new methodologies (both experimental and theoretical) but also providing new opportunities. This session will primarily focus on the application of ion spectroscopy of non-covalent interactions in clusters and biological systems. These include solvent clusters, secondary and tertiary structure of proteins, and weakly-bound molecular clusters. Topics covered will include: structural probes for weak interactions; advances in action spectroscopy; and conformationally selective spectroscopy. A key discussion point will concern the marriage of mass-spectrometery with optical spectroscopy. The interpretation of experimental data obtained for these larger systems demands concomitant developments in theoretical methods, and the session will provide an opportunity for comparative discussions of new theoretical approaches in this field.

Ahmed, Musahid↗

DOE OSTI2014

Amine-Amine Exchange in Aminium-Methanesulfonate Aerosols

Aerosol particles are ubiquitous in the atmosphere and have been shown to impact the Earth’s climate, reduce visibility, and adversely affect human health. Modeling the evolution of aerosol systems requires an understanding of the species and mechanisms involved in particle growth, including the complex interactions between particle- and gas-phase species. Here we report studies of displacement of amines (methylamine, dimethylamine or trimethylamine) in methanesulfonate salt particles by exposure to a different gas-phase amine, using a single particle mass spectrometer, SPLAT II. The variation of the displacement with the nature of the amine suggests that behavior is dependent on water in or on the particles. Small clusters of methanesulfonic acid with amines are used as a model in quantum chemical calculations to identify key structural elements that are expected to influence water uptake, and hence the efficiency of displacement by gas-phase molecules in the aminium salts. Such molecular-level understanding of the processes affecting the ability of gas-phase amines to displace particle-phase aminium species is important for modeling the growth of particles and their impacts in the atmosphere.

atmospheric aerosols↗