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In this work, we present a comprehensive experimental and theoretical study of the vibrational spectra of PAH molecules recently detected in the interstellar medium: 1-cyanonaphthalene and 2-cyanonaphthalene. The room temperature IR spectra of 1- and 2-cyanonaphthalene in the region 100-3100 cm -1 and their vibrational Raman spectra in the region 35-3100 cm -1 are reported here for the first time. A detailed spectral analysis is carried out using quantum chemical calculations employing the DFT methodology. Anharmonic corrections using the VPT2 method yield excellent agreement with the experimental spectra. A re-investigation of the vibrational spectrum of the parent molecule: naphthalene validates the experimental and theoretical methods used. A consistent set of assignments is reported for the fundamental bands of 1- and 2-cyanonapththalene. The experimental and theoretical data presented here would be useful inputs for modelling the role of cyanonaphthalene in astrophysical processes., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Many icy bodies in the solar system have been found to contain a rich mixture of simple molecules on their surfaces. Similarly, comets are now known to be a reservoir of molecules ranging from water to amides. The processing of planetary/cometary ices leads to the synthesis of more complex molecules some of which may be the harbingers of life. Carbon disulphide (CS 2 ) and ammonia (NH 3 ) are known to be present on many icy satellites and comets. Reactions involving CS 2 and NH 3 may lead to the formation of larger molecules that are stable under space conditions. In this paper we present temperature dependent VUV spectra of pure CS 2 in the ice phase, and of CS 2 and NH 3 ices deposited as (i) layered, and (ii) mixed ices at 10 K and warmed to higher temperatures until their sublimation. Pure CS 2 ice is found to have a broad absorption in the VUV region, which is unique for a small molecule in the ice phase. In layered and mixed ices, the molecules tend to affect the phase change and sublimation temperature of each other and also leave behind a form of CS 2 -NH 3 complex after thermal annealing. This study of CS 2 -NH 3 ice systems in layered and mixed configurations would support the detection of these species/complexes in mixed molecular ices analogous to that on planetary and cometary surfaces., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Isoprene and its oligomers, terpenes, are expected to be present, along with other complex organic molecules in the diverse environments of the ISM and in our solar system. Due to insufficient spectral information of these molecules at low temperature, detection and understanding the importance of these molecules has been rather incomplete. For this purpose, we have carried out the vacuum ultraviolet (VUV) photoabsorption measurements on pure molecular ices of isoprene and a few simple terpenes: limonene, α-pinene and β-pinene by forming icy mantles on cold dust analogs. From these experiments, we report the first low temperature (10 K) VUV spectra of isoprene and its oligomers limonene, α-pinene and β-pinene. VUV photoabsorption spectra of all the molecules reported here reveal similarities in the ice and gas phase as expected, with an exception of isoprene where a prominent red shift is observed in the ice phase absorption. This unqiue property of isoprene along with distinctive absorption at longer wavelengths supports its candidature for detection on icy bodies., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

We have irradiated benzene ices deposited at 4 K on a cold, interstellar dust analog with vacuum ultraviolet (9 eV) irradiation for periods lasting from several hours to nearly a day, after which the irradiated ice was warmed to room temperature. Vacuum ultraviolet photoabsorption spectra of the aromatic residue left at room temperature were recorded and showed the synthesis of benzene derivatives. The residue was also imaged using an electron microscope and revealed crystals of various sizes and shapes. The result of our experiments suggests such geometrically shaped dust particles may be a key component of interstellar dust., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Understanding the photochemical behavior of structural isomers of hydroxycoumarin (HC) having different properties of consequence in biological activities demand spectroscopic information of this class of compounds. Barring 6-hydroxycoumarin (6-HC), other isomers of HC's are well studied spectroscopically. To understand and compare the photochemical activity of 6-HC with other isomers, a detailed study of this molecule has been taken up. For this purpose, electronic, vibrational and structural properties of 6-HC have been studied using ultraviolet absorption and Infrared spectroscopy techniques. Quantum chemical calculations have been performed at DFT/B3LYP level of theory to get the optimized geometry and vibrational frequencies of normal modes to support and analyze experimental data. The detailed vibrational assignments were made on the basis of potential energy distributions. Chemical activity, molecular orbital energies, band gap and hyper-polarizability information have been computed from quantum chemical simulations. NBO analysis helped in understanding the stability of the molecule arising from hyper-conjugative interaction and charge delocalization. UV-Visible spectrum of the compound was recorded in the region 300-600 nm helped in obtaining band gap data of the compound. Molecular Electrostatic Potentials (MESP) were plotted and the respective centers of electrophilic and nucleophilic attacks were predicted with the help of Fukui functions calculations. Further, it was observed that the negative electrostatic potential regions are mainly localized over the oxygen atoms and the positive regions are localized over the benzene ring. Details of the results and analysis of experimental and theoretical spectroscopy studies are presented in this paper., (Copyright © 2019 Elsevier B.V. All rights reserved.)