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4 results on '"SPECTROSCOPIC FINGERPRINTS"'

1. Comparative study using spectroscopic and mineralogical fingerprinting for suspended sediment source apportionment in a river–reservoir system.

Author

Das, Arnab, Remesan, Renji, Chakraborty, Somsubhra, Collins, Adrian L., and Gupta, Ashok Kumar

Subjects
SUSPENDED sediments, SOIL conservation, FARMS, HUMAN settlements, LAND use
Abstract

The need to control soil erosion has received increasing attention, but quantitative data on the sources of suspended sediment in many river–reservoir systems is still lacking. The goal of this research was to compare the application of spectroscopic [mid‐infrared (MIR)] and mineralogical [X‐ray diffraction (XRD)] fingerprints for assessing relative sediment source contributions from different land use groups (agricultural lands, forests and human settlements) in the Konar–Damodar river–reservoir system in India. Source apportionment was estimated using partial least square (PLS) regression for spectroscopic tracers (MIR) and the Bayesian MixSIAR model for mineralogical tracers. Both methods identified differences between the pre‐ and post‐monsoon sediment contributions of forests (overall contribution bounds of ~35–43%). During monsoon seasons, both fingerprinting methods indicated agricultural land use as the primary source of suspended sediment. Although there were some temporal variations in the predicted contributions of the land use sources, the MIR‐PLS and mineralogical–MixSIAR methods produced comparable ranges. The respective variations in contributions, using MIR‐PLS and mineralogical–MixSIAR, were ~31 to 66% compared with ~36 to 61% for agricultural lands, ~21 to 43% compared with ~15 to 39% for forests and ~16 to 37% compared with ~19 to 32% for human settlements. [ABSTRACT FROM AUTHOR]

Published
2024
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2. Modelling Photoionisation in Isocytosine: Potential Formation of Longer‐Lived Excited State Cations in its Keto Form

Author

Segarra‐Martí, Javier, Bearpark, Michael J., and European Commission

Subjects
Models, Molecular, CASPT2, Ultraviolet Rays, ADN, Physics, Atomic, Molecular & Chemical, RELAXATION DYNAMICS, CASSCF, Article, Cytosine, MOLECULAR WAVE-FUNCTIONS, Cations, IMPLEMENTATION, 0307 Theoretical and Computational Chemistry, Physical and Theoretical Chemistry, 0306 Physical Chemistry (incl. Structural), Radiació ionitzant, Science & Technology, Chemical Physics, Molecular Structure, Chemistry, Physical, Conical Intersections, Physics, SPECTROSCOPIC FINGERPRINTS, DNA, Articles, Ketones, Photochemical Processes, URACIL, Atomic and Molecular Physics, and Optics, Chemistry, Photostability, 2ND-ORDER PERTURBATION-THEORY, Photoionisation, Physical Sciences, ANO BASIS-SETS, SIMULATION, 0202 Atomic, Molecular, Nuclear, Particle and Plasma Physics, CASSCF/CASPT2, RNA, ELECTRON CORRELATION, DNA/RNA
Abstract

Studying the effects of UV and VUV radiation on non‐canonical DNA/RNA nucleobases allows us to compare how they release excess energy following absorption with respect to their canonical counterparts. This has attracted much research attention in recent years because of its likely influence on the origin of our genetic lexicon in prebiotic times. Here we present a CASSCF and XMS‐CASPT2 theoretical study of the photoionisation of non‐canonical pyrimidine nucleobase isocytosine in both its keto and enol tautomeric forms. We analyse their lowest energy cationic excited states including 2π+ , 2nO+ and 2nN+ and compare these to the corresponding electronic states in cytosine. Investigating lower‐energy decay pathways we find – unexpectedly ‐ that keto‐isocytosine+ presents a sizeable energy barrier potentially inhibiting decay to its cationic ground state, whereas enol‐isocytosine+ features a barrierless and consequently ultrafast pathway analogous to the one previously found for the canonical (keto) form of cytosine+. Dynamic electron correlation reduces the energy barrier in the keto form substantially (by ∼1 eV) but it is nevertheless still present. We additionally compute the UV/Vis absorption signals of the structures encountered along these decay channels to provide spectroscopic fingerprints to assist future experiments in monitoring these intricate photo‐processes., The photostability of isocytosine upon ionising radiation exposure is assessed theoretically in both keto and enol tautomeric forms. This non‐canonical base, which features analogous UV excited state reactivity to DNA nucleobase cytosine, unexpectedly displays sizeable energy barriers along the cationic excited state in its keto form that hamper the decay. Simulations suggest isocytosine is less photostable against photoionisation, a factor that might contribute to selecting the more resilient cytosine under prebiotic VUV radiation exposure.

Published
2021

3. pH-Specific Halide-Dependent Materials from ZrIV/Hydroxycarboxylic Acid/Aromatic Chelator Reactivity: Architecture-Lattice Dimensionality and Spectroscopic Fingerprint Relations.

Author

Halevas, Eleftherios, Karamelidou, Asimenia, Hatzidimitriou, Antonios, Mateescu, Constantin, and Salifoglou, Athanasios

Subjects
*HALIDES, *HALOGEN compounds, *ZIRCONIUM, *TITANIUM group, *CARBOXYLIC acids
Abstract

The chemical reactivity of binary and ternary ZrIV/hydroxycarboxylic acid/(N,N-aromatic chelator) systems (hydroxycarboxylic acid = citric, malic acid; N,N-aromatic chelator = 1,10-phenanthroline) has been investigated in a pH-specific manner, giving rise to the new binary and ternary crystalline materials [Zr2F6(C6H4O7)2](CH6N3)6 ·H2O ( 1), [Zr2F6(C4H3O5)2](NH4)4 ·3H2O ( 2), [Zr2(C4H3O5)2(C4H4O5)2(C4H5O5)2](CH6N3)4 ·4.5H2O ( 3), and [Zr2(C4H3O5)2(C4H4O5)2(C4H5O5)2](C12H8N2)(C12H9N2)2(CH6N3)2 ·6H2O ( 4). Compounds 1- 4 were characterized by elemental analysis, FTIR spectroscopy, TGA, 13C-CPMAS, 19F-DPMAS, and 1H CRAMPS NMR spectroscopy, and X-ray crystallography. The structures of 1- 4 reveal the influence of fluoride in the starting ZrIV reagents on the identity of the Zr2O2-containing dinuclear assemblies in the arisen 3D architectures. The uniquely defined spectroscopic data, including the NMR data, corroborate the X-ray structures of 1- 4 and reflect the contribution of the intra/intermolecular interactions to the structural speciation of the investigated systems. Collectively, the work 1) depicts the factors that determine the nature and properties of the emerging synthetic materials in the investigated systems, 2) formulates structural architecture-lattice dimensionality and spectroscopic fingerprint correlations, and 3) projects the framework through which new ZrIV materials with defined physicochemical properties can arise at the binary and ternary level. [ABSTRACT FROM AUTHOR]

Published
2015
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4. Metastable Molecules in the Ground and in Excited States, Theory Development, Implementation and Application

Author

FLORIDA UNIV GAINESVILLE, Bartlett, Rodney J., FLORIDA UNIV GAINESVILLE, and Bartlett, Rodney J.

Abstract

Our work for the AFOSR has three primary components: Development of new quantum theory for the accurate description of molecular structure and spectra. Implementation of this new theory into general purpose computer programs (ACES II and pralel ACES III) to make it possible for many investigators, besides ourselves, to readily apply these new methods to problems of their interest. Application of these new methods to challenging molecules chosen to test the new methods, and to other systems of interest to AFOSR. These include high energy, density molecules, where the new methods allow an assessment of their energy content, stability, possible synthetic paths, activation barriers, and provide spectroscopic fingerprints for identification. We also make applications of interesting clusters, atmospheric systems, potential interstellar molecules, and to gas phase molecular reactions of the sort that can occur in flames., The original document contains color images.

Published
2006

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