Trends In Spectroscopy Research Articles

New trends in spectroscopy of solid nitrogen

This topical review presents new trends in emission spectroscopy of solid nitrogen. Developed approach to study of charged centers and their role in radiation-induced phenomena as well as relaxation processes is discussed. The emission spectroscopy elaborated incorporates correlated in real time detection of several relaxation emission—optical photons, electrons and emission of particles. Key details of this approach applied in research of pre-irradiated by electron beam solid nitrogen and nitrogen-helium nanoclusters grown by a gas jet condensation technique are given. New methods—nonstationary luminescence and nonstationary desorption, designed to study ion-electron recombination reactions—are briefly presented. The selected recent results obtained employing this approach and emission spectroscopy techniques to study the charge related phenomena in condensed nitrogen are summarized. Main attention is given to detection of polyatomic ionic centers containing four and three nitrogen atoms: N4+,N3+,N3−. Their part played in radiation-induced phenomena and relaxation processes, in particular desorption, is discussed.

Probing the Photodynamics of Rhodopsins with Reduced Retinal Chromophores.

While the light-induced population dynamics of different photoresponsive proteins has been investigated spectroscopically, systematic computational studies have not yet been possible due to the phenomenally high cost of suitable high level quantum chemical methods and the need of propagating hundreds, if not thousands, of nonadiabatic trajectories. Here we explore the possibility of studying the photodynamics of rhodopsins by constructing and investigating quantum mechanics/molecular mechanics (QM/MM) models featuring reduced retinal chromophores. In order to do so we use the sensory rhodopsin found in the cyanobacterium Anabaena PCC7120 (ASR) as a benchmark system. We find that the basic mechanistic features associated with the excited state dynamics of ASR QM/MM models are reproduced using models incorporating a minimal (i.e., three double-bond) chromophore. Furthermore, we show that ensembles of nonadiabatic ASR trajectories computed using the same abridged models replicate, at both the CASPT2 and CASSCF levels of theory, the trends in spectroscopy and lifetimes estimated using unabridged models and observed experimentally at room temperature. We conclude that a further expansion of these studies may lead to low-cost QM/MM rhodopsin models that may be used as effective tools in high-throughput in silico mutant screening.

Primary Amine Stabilization of a Dicopper(III) Bis(μ-oxo) Species: Modeling the Ligation in pMMO

Here we report the formation of the first examples of dicopper(III) bis(μ-oxo) complexes ligated by the primary amines, propylenediamine, and N,N,-dimethyl propylenediamine. Stabilization of these new compounds is effected at -125 °C by "core capture"- introduction of exogenous ligand to a preformed dicopper(III) bis(μ-oxo) complex supported by the peralkylated tetramethyl propylenediamine. Primary amine ligation in these compounds matches the single primary amine coordination of the putative active site of particulate methane monooxygenase (pMMO) and polysaccharide monooxygenase. Reactivity studies presented here show primary amine ligated cores are competent oxidants, capable of activating C-H bonds by an H-atom abstraction mechanism. Trends in spectroscopy, structure, and reactivity provide hints to the potential role of primary amine ligation in pMMO: increased substrate accessibility to the redox active orbitals of the Cu2O2 core and greater stabilization of the oxidant without attenuation of oxidizing power.

Opening remarks to the symposium, “Future trends in spectroscopy”

Opening remarks to the symposium, “Future trends in spectroscopy”

The dissemination of the results of scientific research in the era of electronic media

This paper is the extended text of a lecture presented during an “on-invitation” symposium: “ Future Trends in Spectroscopy”, organized on the occasion of the 50th Anniversary of the founding of Spectrochimica Acta. This symposium was held under the auspices of the Pontificia Academia Scientiarum in the Casina Pio Quattro in Vatican City. The lecture considers the future of scientific publishing primarily from the point of view of the actual behaviour of authors, editors, reviewers, publishers, and readers. In this scope the author discusses (a) aims and format of scientific publications, (b) new approaches to conventional scientific publishing, i.e., in “hardcopy journal format”, (c) the implications of desktop publishing (DTP) and camera-ready copy (CRC) for author, editor, reviewer, and publisher, and (d) the truly electronic publication, i.e., a publication on an electronic medium, such as a diskette, which does not only contain text and graphics, but also executable programs, source codes, data files, and parameter sets. The paper includes a tutorial discussion of issues such as word processors, scientific word processors, DTP, WYSIWYG (What You See Is What You Get) versus ML (Markup Language), procedural markup versus descriptive markup, text versus graphics, and standard generalized markup language (SGML). As to conventional scientific publishing the author concludes that the “DTP-CRC approach” is not a viable alternative. The most promising appears an approach in which the author produces the “author's primary electronic manuscript” (APEM) in ASCII format with graphics in a format such as Computer Graphics Metafile (CGM) without procedural markup but with a minimum of descriptive markup, for example, in SGML codes. The “APEM-SGML approach” is considered (i) to provide for a balanced distribution of tasks among authors, editors, reviewers, and publishers, (ii) to eliminate the necessity of rekeying documents, and (iii) to give publishers additional “handles” to exploit the information via on-line and CD-ROM databases. This appears to be the solution that will make every shoecobbler stick to his last and thus feel entirely comfortable. As to the truly electronic publication, the author feels that there must be excellent perspectives for an electronic spectroscopy journal and proposes to investigate the viability of a journal Spectrochimica Acta Electronica (SAE), as a supplement of Parts A and B.