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Gaseous ion spectroscopy generally couples mass spectrometry with a class of high-resolution laser spectroscopy, providing a route for studying the intrinsic chemical and physical properties of isolated ions. The isolation of the molecular ion of interest from its native environment is important to decouple the influence of the surroundings from the intrinsic properties. The effect of the environment can then be incrementally re-introduced through studies of sequentially solvated clusters, which allow the interaction with solvent molecules with the ion to be studied on the molecular level. This field has the potential to impact a wide range of chemical, physical and biological problems and it has seen a rapid diversification in the past decade with the application of different ion sources, cryogenic ion traps, and new light sources such that this potential impact is rapidly being realised. The rapid development of experimental techniques has required a concomitant development of theory, which is now being used to model ever larger systems both in terms of structure and dynamics.
 
The rapid growth of the field and impressive scientific achievements over the past decade make this meeting both timely and topical and we hope will provide a roadmap of where the field is and what the challenges will be over the next 5-10 years and beyond. The meeting sessions will be structured by technique developments and within these sessions, the various broad applications will be discussed, along with the associated state-of-the-art theoretical methods.

Format

The Faraday Division have been organising high impact Faraday Discussions in rapidly developing areas of the physical sciences, with a focus on physical chemistry and its interfaces with other scientific disciplines for over 100 years

Faraday Discussions have a special format where research papers written by the speakers are distributed to all participants before the meeting, and most of the meeting is devoted to discussing the papers. Everyone contributes to the discussion - including presenting their own relevant research. The research papers and a record of the discussion are published in the journal Faraday Discussions.

Aims

The purpose of this Faraday Discussion is to bring together experimentalists and theoreticians working on ion spectroscopy in a broad sense and to provide a forum to discuss the latest innovations and applications. These will range from the IR spectroscopy and anion formation mechanism of molecules in the interstellar medium, to the intrinsic structure of catalytic centres in chemical reactions, to the ultrafast dynamics of bioactive chromophores, to exotic ionic systems such as Coulombic crystals and dipole-bound anions.

Themes

• Controlling internal degrees

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.

• Pushing resolution in frequency and time 

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.

• Going larger: Complex molecules and probing interactions with the environment.

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.

• Exotic systems

Gaseous ions provides routes to studying exotic molecular systems. These including Coulomb crystals, multiply-charged ions (anions and cations), solvated electrons, resonances, and dipole-, multipole-, or correlation-bound anions. Spectroscopy on such systems yields deep insight into the interactions that hold them together and they can be used as new spectroscopic tools. This session will explore the spectroscopy of exotic ionic systems and their application to new methods.  Exotic molecular systems provide challenging targets that push the limits of current theoretical methodologies, so the session will discuss new theoretical approaches that accurately predict the characteristics of exotic systems.