Acetylene is considered to be an important molecule for spectroscopic research due to its role in environ-mental chemistry, astrophysics, biochemistry and photochemistry of various planets. The high resolution spectroscopic studies of acetylene (12C2H2) in the 6474-6515 cm -1 spectral range have been performed using in-house developed external-cavity diode laser absorption spectroscopy technique. The study is fo-cused on experimental measurement of self-broadening coefficients (yself) and line intensities of 27 l -doublet ro-vibrational lines belonging to the P-branch transition of v1 + v3 + v4 - v4 hot band lying in the 6474-6515 cm -1 spectral range. The yself and line intensity have been retrieved by modelling of each experimentally observed rotational line with standard Voigt line profile using custom written python based computer program. The measured yself and line intensities were compared with the values present in HITRAN2020 database, showing mean difference of about-1.9% and 2.48%, respectively. In contrast to the line intensity, where rotational and symmetry dependency are readily visible, yself exhibits only ro-tational dependency. The l-type doubling constants of both v1 + v3 + v4 and v4 states of v1 + v3 + v4 - v4 hot band have also been obtained. Detailed understanding of these molecular parameters will play an important role in modelling of planetary atmospheres.(c) 2023 Elsevier Ltd. All rights reserved.

Hydrogen sulphide (H2S) is an extremely hazardous gas which leads to poisoning at higher concentration. Here, we demonstrate the trace detection and line intensity measurement of H2S by means of efficient and indigenously developed off-axis integrated cavity output spectroscopy (OA-ICOS) technique coupled with an external cavity diode laser operating in near-infrared spectral region. Trace detection of H2S was made with OA-ICOS absorbance spectra of ro-vibrational line (51, 5 -> 61, 6 & 50, 5 -> 60, 6) centered at - 6344 cm-1 of v1 + v2 + v3 band. A - 600 ppbv limit of detection was achieved for an averaging time of 350 s with Allan deviation analysis. Additionally, line intensities of several degenerate R branch transitions of v1 + v2 + v3 band including 51, 5 -> 61, 6 & 50, 5 -> 60, 6 transition was experimentally measured with OA-ICOS. The study will be valuable in aiding the spectroscopic databases of H2S and have potential application in extracting molecular concentrations in the planet's atmospheres.

Cavity ring-down spectroscopy (CRDS) is a highly sensitive laser absorption spectroscopic technique. In this paper, we report the pulsed CRDS study of nitrogen dioxide (NO2) using an home-built CRDS set-up. Pulsed CRDS measurements of diluted NO2 gas (0.091% in N-2) at various low pressures have been carried out in 501-506 nm spectral range. From the CRDS measurements, molecular spectral features of NO2 at very low partial pressure, similar to 10 mTorr (3.42 x 10(14) molecules/cm(3)), was evidently observed. CRDS ring-down decay measurements carried out at wavelength of 504.76 nm for various molecular concentrations of NO2 demonstrate a minimum detectable number density of NO2 of 8.65 x 10(12) molecules/cm(3), which would correspond to 350 ppbv under atmospheric condition. 40 ppbv of detection limit of NO2 is estimated from the standard deviation (1 sigma) of ring-down decay time measurements at 504.76 nm wavelength. Absorption and integrated absorption cross section of NO2 are also estimated.

Trans-urocanic acid (t-UCA) is an important epidermal UV protector predominantly found in human skin. Exposure of UV radiation triggers photoisomerization of t-UCA into its other conformer, cis-urocanic acid (cis-UCA), which has been shown to be a mediator of UV-induced immune-suppression leading to skin cancer. In this report, we present the investigation of molecular changes of t-UCA under high pressures by in-situ high pressure Raman spectroscopy. The study indicates onset of ring opening polymerization of t-UCA at pressure above 1.4 GPa. At pressures beyond 5 GPa, a well discernible characteristic vibrational mode (CC stretch) accompanied by several other spectral features such as δ CO2- and δ NH modes of cis-UCA point towards the isomerization of residual t-UCA monomers into cis-UCA. The content of cis-UCA gradually increased with increase in pressure. On release to ambient conditions, the spectrum of the quenched sample showed Raman modes of polymer and cis-UCA indicating that the changes are irreversible.

The high-resolution infrared absorption study of polyatomic molecules is of great interest. Availability of intense sources in infrared region and with the progress made in theoretical techniques, it is possible to do line by line analysis of polyatomic spectrum. Many a times, the analysis of high-resolution spectra requires the inclusion of various vibration–rotation interactions. Sometimes the interacting state could be a state to which transitions are not observed in the spectrum called as “shadow” state. In this article, we present the results of the analysis of ΔJ = 0, ±1; ΔK = ±1 sub-bands with Kmax = 3 and Jmax = 45 of the high-resolution spectrum of ν7 band of CH3CCD molecule for the first time. The room temperature Fourier transform infrared (FTIR) spectrum of CH3CCD in the region 1300–1600 cm−1 was recorded at an apodized resolution of 0.004 cm−1 which covers the ν7 fundamental band of CH3CCD. Approximately 1500 rotational lines consisting of total of 12 sub-bands of ν7 band of CH3CCD have been assigned. The rovibrational analysis has been carried out by taking into account the strong x–y Coriolis interaction of the ν7 = 1 state with the ν4 = 1 “shadow” state. The band center and the rotational constants, B and (A–B) of ν4 = 1 state were also derived accurately from the perturbation analysis in this work.

Surface-enhanced Raman scattering (SERS) study carried on thiazolidine-2,4-dione (TZD), a pharmacologically active heterocyclic compound, points to the presence of TZD dimer formed by plasmon-induced dimerization reaction of TZD on the surface of silver nanoparticles (Ag NP) at TZD concentrations of 10-3 M and above. The evidence for the presence of dimer was obtained from the appearance of a prominent band at 1566 cm-1 corresponding to the ν(C═C) band (a characteristic vibrational band observed for the Knoevenagel condensation reaction products) which is absent in the normal Raman scattering (NRS) spectra of TZD solid/solution. The observed spectrum compares well with the calculated spectrum of dimer obtained using density functional theory (DFT) calculations. The dimerization reaction is plausibly induced by the transfer of hot electrons generated by the nonradiative plasmon decay of Ag NP, and the proposed reaction mechanism is discussed. However, at lower concentrations (10-4-10-6 M), the characteristic dimer peak (1566 cm-1) is absent and the SERS spectra resemble more the NRS spectrum of TZD with a few changes. The spectral analysis supported by DFT calculations showed that TZD molecules undergo deprotonation and get adsorbed on the Ag NP surface as enolate forms. The proximity of TZD molecules on the surface of Ag NP is a necessary factor for the dimerization to occur. At lower concentrations, most molecules lie apart and reactions between molecules become less feasible, and they remain as monomers on the surface, while at higher concentrations the molecules are closer to each other on the Ag NP surface favoring the dimerization reaction to take place, leading to the formation of the dimer.

Effect of TiO2 addition in Cs containing Sodium-borosilicate glasses is studied using Raman and infrared spectroscopic techniques. As revealed from infrared and Raman studies, TiO2 does not form segregated phase, but instead enters into the borosilicate network. It is further observed that TiO2 addition results in modifications of the borate and silicate structural units by transforming into tetraborates and metasilicate structural units. These structural modifications are responsible for Cs immobilization, leach rate and chemical durability of these glasses.

The high-resolution Fourier transform spectrum of propyne-d3 (CD3CCH) at room temperature has been recorded in the region of the ν7 band (950–1200 cm−1) at an apodized resolution of 0.004 cm−1. About 2400 lines consisting of a total of 25 sub-bands ranging from KΔK = −13 to 12 have been assigned in the ν7 band of CD3CCH. In the fitting analysis, the ν4 = 1 state to which transitions have not been identified in the experimental spectrum included as a "shadow" state. The data have been analyzed taking into account of the strong x-y Coriolis interaction of the ν7 = 1 state with the ν4 = 1 state. l-type interactions between the ±l components of the ν7 = 1 state, and a weak k-type doubling interaction between ν7 = 1 and ν4 = 1 states have been included in the analysis. The vibration-rotation transitions for K ≥ 8 show fairly large amount of deviation and most likely interacted by other nearby states. The transitions upto K = 7 and Jmax = 61 could be fitted with a standard deviation of 0.0007 cm−1.

Surface-enhanced infrared absorption (SEIRA) studies of cytosine adsorbed on the thermally evaporated gold film on CaF2 have been carried out in transmission mode. SEIRA spectrum down to 0.1 mu M was observed owing to the plasmonic effect of the gold nano film. Cytosine molecules appear to adsorb on the film via C=O and NH groups as evidenced by the red shift observed in the stretching vibrations of the above groups. The molecules assume a perpendicular orientation with respect to the surface.

The high-resolution Fourier transform spectrum of propyne-d(3) (CD3CCH) at room temperature has been recorded in the region of the v(7) band (950-1200 cm(-1)) at an apodized resolution of 0.004 cm-1. About 2400 lines consisting of a total of 25 sub-bands ranging from K Delta K= 13 to 12 have been assigned in the v(7) band of Cd3CCH. In the fitting analysis, the v(4) = 1 state to which transitions have not been identified in the experimental spectrum included as a "shadow" state. The data have been analyzed taking into account of the strong x-y Coriolis interaction of the v(7) =1 state with the v(4) = 1 state. 1-type interactions between the I components of the v(7) = 1 state, and a weak k-type doubling interaction between v(7) = 1 and v(4) = 1 states have been included in the analysis. The vibration-rotation transitions for K >= 8 show fairly large amount of deviation and most likely interacted by other nearby states. The transitions upto K= 7 and J(max) = 61 could be fitted with a standard deviation of 0.0007 cm-1. (C) 2017 Elsevier Inc. All rights reserved.

Pd/reduced graphene oxide (Pd-RGO) composites were successfully prepared from graphite and PdCl2 precursors using wet impregnation and reverse micro emulsion methods. From hydrogen adsorption studies it is confirmed that spillover of hydrogen from Pd to graphene layers occurs at room temperature. However, at low temperatures there is negligible spillover effect and this is explained based on lower kinetic energy available with hydrogen atoms to overcome the activation barrier involved in diffusion. Detailed 13C MAS NMR and Raman spectroscopic studies confirmed that small amounts of structural units (functional groups) like carboxylate and polyacetylenic linkages are retained in Pd-RGO samples prepared by wet impregnation and reverse micro-emulsion methods, respectively. Such structural moieties facilitate the atomic scale mixing of Pd with the graphene layers thereby improving the spillover efficiency.

Structural evolution of turbostratic carbon samples as a function of annealing temperature has been investigated in detail using small angle X-ray scattering (SAXS), solid state nuclear magnetic resonance (NMR) and Raman spectroscopic techniques. From these studies, it is established that, samples heated at lower temperatures (700 degrees C and 800 degrees C) consist carbon particles with rough surfaces forming structure of surface fractal in nature. Whereas the sample heated at higher temperature (900 degrees C) consists of larger clusters with nearly smooth surface as well as smaller size particles forming dense mass fractal structure. For this sample, solid state NMR and Raman Spectroscopic studies indicate an increased extent of overlapping of 2p(z) orbital of carbon atoms due to improved long range ordering and clustering. Hydrogen adsorption studies further substantiated that energetically more homogeneous surface exists for particles of 900 degrees C heated sample as compared to those of 700 degrees C and 800 degrees C heated samples. A highest hydrogen storage capacity of 0.152 H/M has been observed at 123 K and 45 bar pressure for the sample heated at 900 degrees C. (C) 2016 Elsevier Masson SAS. All rights reserved.

Different polymorphs of Li2MnSiO4 were synthesized by controlled calcination at 500, 750 and 1000 degrees C. XRD studies suggest formation of Pmnb (gamma) -orthorhombic, Pmn2(1) (beta) - orthorhombic and P2(1)/n (gamma) - monoclinic structures at these temperatures. Infrared studies of these polymorphs suggests differences in the arrangement of SiO4, MnO4 and LiO4 units, and the inequivalent sites of Li+ responsible for better electrochemical performance of Pmn2(1).

A titania mineral (obtained from East coast, Orissa, India) was investigated by X-ray diffraction (XRD), photoacoustic spectroscopy (PAS), Raman and Electron Paramagnetic Resonance (EPR) studies. XRD studies indicated the presence of rutile (91%) and anatase (9%) phases in the mineral. Raman investigation supported this information. Both rutile and anatase phases have tetragonal structure (rutile: space group P42/mnm, a = 4.5946(1) Å, c = 2.9597(1) Å, V = 62.48(1) (Å)3, Z = 2; anatase: space group I41/amd, 3.7848(2) Å, 9.5098(11) Å, V = 136.22(2) (Å)3, Z = 4). The deconvoluted PAS spectrum showed nine peaks around 335, 370, 415,485, 555, 605, 659, 690,730 and 785 nm and according to the ligand field theory, these peaks were attributed to the presence of V4+, Cr3+, Mn4+ and Fe3+ species. EPR studies revealed the presence of transition metal ions V4+(d1), Cr3+(d3), Mn4+(d3) and Fe3+(d5) at Ti4+ sites. The EPR spectra are characterized by very large crystal filed splitting (D term) and orthorhombic distortion term (E term) for multiple electron system (s > 1) suggesting that the transition metal ions substitute the Ti4+ in the lattice which is situated in distorted octahedral coordination of oxygen. The possible reasons for observation of unusually large D and E term in the EPR spectra of transition metal ions (S = 3/2 and 5/2) are discussed.

Eu3+ doped alpha-Ga2O3 and beta-Ga2O3 nanorods were prepared by heating Eu3+ doped GaOOH nano-rods at 500 and 900 degrees C respectively. XRD patterns and infrared spectra revealed that the sample are crystalline upto 5 at % Eu3+ incorporation in beta-Ga2O3 Unlike this in the case of alpha-Ga2O3, incorporation of Eu above 0.5 at % resulted in the amorphisation of crystalline Ga2O3 phase. This is explained in terms of the difference in the coordination of Ga in alpha and beta forms of Ga2O3.

Aluminized and thermally oxidized Alloy 690 specimen containing Al2O3 layer on the outermost surface and bare alloy substrates were exposed either in nitrate-based simulated nuclear waste solution at 373K for 216h or sodium borosilicate melt at 1248K for 192h. The exposed samples were characterized by micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Aluminized and thermally oxidized sample exposed to simulated nuclear waste indicated the presence of Al2O3, mixed oxides of NiCr2O4 and NiFe2O4, NiO, a small amount of Cr2O3, mixed oxides of Cr+3 and Cr+6 and elemental aluminium. Similar surface compositions were recorded for coated samples exposed to sodium borosilicate melt. The formation of mixed oxides on coated samples could be attributable to oxidation treatment. Bare Alloy 690 substrates exposed to simulated nuclear waste, indicated the presence of γ-Fe2O3, NiO, a small amount of Cr2O3, mixed oxides of Cr+3 and Cr+6, elemental chromium and nickel. The alloy substrate exposed to sodium borosilicate melt showed similar compositions along with presence of CrO3, mixed oxides of NiCr2O4 and NiFe2O4. The presence of mixed oxides on bare alloy substrate exposed to molten glass resulted from high temperature exposure.

Nano-crystalline and bulk Y2Sn2O7 particles were prepared based on polyol method followed by heating at 700, 900 and 1200 °C. Structural differences in the bulk and nanoparticles were investigated using XRD, Raman and 119Sn MAS-NMR techniques. From these results it is inferred that the environment of SnO6 octahedra in Y2Sn2O7 nanoparticles is significantly distorted in nanoparticles compared to bulk. Further, unlike in bulk Y2Sn2O7 there exists strong anisotropy in Sn-O bond lengths in nanoparticles of Y2Sn2O7.

Aluminized and thermally oxidized Ni-Cr-Fe based superalloy 690 substrates with Al2O3 layer on top have been exposed in nitrate based environment (simulated high level nuclear liquid waste) at 373 K for 216 hours and sodium borosilicate melt at 1248 K for 192 hours. The surfaces of exposed samples have been characterized by using Electron probe micro-analyzer (EPMA). Elemental X-ray mapping on coated specimen that exposed in simulated nuclear waste solution revealed that the surface is enriched with Ni, Cr and Al. X-ray mapping on surface of the specimen that interacted with sodium borosilicate melt indicated that the surface is composed of Al, Fe, Ni and Cr.

Surface-enhanced infrared absorption (SEIRA) studies of uracil adsorbed on wet-chemically prepared gold nanoparticles (AuNp) immobilized on silanised glass substrate were carried out using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. The deposition time dependent evolution of morphological changes in AuNp films and its influence on the SEIRA spectra of uracil were investigated. The morphological changes were examined by atomic force microscopy (AFM). The spectrum of uracil adsorbed on AuNp film obtained with 1/2 an hour deposition time showed a clear enhancement than 2 and 4h deposition times. The small shift seen in SEIRA spectra indicates weak interaction of the molecules with AuNp film.

The high-resolution Fourier transform spectrum of methyl acetylene-d(1) (CH3CCD) at room temperature has been recorded in the region of the v(3) band (1980-2035 cm(-1)) at an apodized resolution of 0.004 cm(-1). About 600 vibration-rotation transitions have been assigned, with J upto 36 and K upto 6. The spectrum shows the presence of several perturbations. The observed minus calculated deviation of the fit for K = 4 subband is much more than the expected, shows the presence of Fermi resonance with the nearby vibrational state. (C) 2014 Elsevier Inc. All rights reserved.