Pragya Bhatt

Bio: Pragya Bhatt is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Ion & Dissociation (chemistry). The author has an hindex of 7, co-authored 41 publications receiving 142 citations.

Three-body dissociation of OCS3+: Separating sequential and concerted pathways

Abstract: Events from the sequential and concerted modes of the fragmentation of OCS3+ that result in coincident detection of fragments C+, O+, and S+ have been separated using a newly proposed representation An ion beam of 18 MeV Xe9+ is used to make the triply charged molecular ion, with the fragments being detected by a recoil ion momentum spectrometer By separating events belonging exclusively to the sequential mode of breakup, the electronic states of the intermediate molecular ion (CO2+ or CS2+) involved are determined, and from the kinetic energy release spectra, it is shown that the low lying excited states of the parent OCS3+ are responsible for this mechanism An estimate of branching ratios of events coming from sequential versus concerted mode is presented

Formation of H 2 + and H 3 + in energetic highly-charged-ion collisions with NH 3

Abstract: The dissociation of ${\mathrm{NH}}_{3}$ is studied using energetic $\mathrm{H}{}^{+}$ and ${\mathrm{Ar}}^{q+}$ ($q=1,8$) ions. The multi-ion coincidence technique along with the time- and position-sensitive measurements of the recoil ions allows us to distinguish different dissociation channels involving the rearrangement of hydrogen atoms. It is observed that the bond dissociation of ${\mathrm{NH}}_{3}{}^{x+}$ ($x=3--5$) occurs in a concerted manner and nonplanar dissociation exists. Our results indicate a competition between the bond-rearrangement and Coulomb repulsion processes in ${\mathrm{NH}}_{3}{}^{x+}$. Ab initio intrinsic reaction coordinate calculations are performed to understand the bond-rearrangement process in ${\mathrm{NH}}_{3}{}^{2+}$.

Kinematics and dissociation dynamics of a water molecule under the impact of 10?keV electrons

Abstract: The kinematics and dissociation dynamics of a H2O molecule induced by 10 keV electrons are studied using a time-of-flight mass spectrometer in conjunction with a position-sensitive detector in multi-hit coincidence mode. Five dissociative channels arising from the complete as well as the incomplete Coulomb explosions of H2Oq+ (q = 2, 3) ions are observed and identified. The dissociation mechanisms (concerted and/or sequential) for these channels are examined. Further, the angular correlation of different fragment ions and the geometrical structure of the precursor ion are studied. The kinetic energy release distributions for the observed channels are also determined. It is found that the pure Coulomb explosion model is insufficient to explain the observed kinetic release distributions. The mean kinetic energy release for these channels is compared with the available data reported by earlier workers who have employed different charged projectiles and sources of photons.

Momentum mapping spectrometer for probing the fragmentation dynamics of molecules induced by keV electrons

Abstract: We describe a new experimental setup for studying the fragmentation dynamics of molecules induced by the impact of keV electrons using the well-known technique of recoil ion momentum spectroscopy. The apparatus consists of mainly a time- and position-sensitive multi-hit particle detector for ion analysis and a channel electron multiplier detector for detecting the ejected electrons. Different components of the setup and the relevant electronics for data acquisition are described in detail with their working principles. In order to verify the reliable performance of the setup, we have recorded the collision-induced ionic spectra of the CO2 molecule by the impact of keV electrons. Information about the ion pairs of CO+:O+, C+:O+ and O+:O+ resulting from dissociative ionizing collisions of 20 and 26 keV electrons with a dilute gaseous target of CO2 molecules has been obtained. Under conditions of the present experiment, the momentum resolutions of the spectrometer for the combined momenta of CO+ and O+ ions in the direction of the time-of-flight axis and perpendicular to the direction of an electron beam are found to be 10.0 ± 0.2 and 15.0 ± 0.3 au, respectively.

Doubly-charged ions in the planetary ionospheres: a review

Abstract: This paper presents a review of the current knowledge on the doubly-charged atomic and molecular positive ions in the planetary atmospheres of the Solar System. It is focused on the terrestrial planets which have a dense atmosphere of N2 or CO2, i.e. Venus, the Earth and Mars, but also includes Titan, the largest satellite of Saturn, which has a dense atmosphere composed mainly of N2 and a few percent of methane. Given the composition of these neutral atmospheres, the following species are considered: C++, N++, O++, CH4++, CO++, N2++, NO++, O2++, Ar++ and CO2++. We first discuss the status of their detection in the atmospheres of planets. Then, we provide a comprehensive review of their complex and original photochemistry, production and loss processes. Synthesis tables are provided for those ions, while a discussion on individual species is also provided. Methods for detecting doubly-charged ions in planetary atmospheres are presented, namely with mass-spectrometry, remote sensing and fine plasma density measurements. A section covers some original applications, like the possible effect of the presence of doubly-charged ions on the escape of an atmosphere, which is a key topic of ongoing planetary exploration, related to the evolution of a planet. The results of models, displayed in a comparative way for Venus, Earth, Mars and Titan, are discussed, as they can predict the presence of doubly-charged ions and will certainly trigger new investigations. Finally we give our view concerning next steps, challenges and needs for future studies, hoping that new scientific results will be achieved in the coming years and feed the necessary interdisciplinary exchanges amongst different scientific communities.

Turning a native or corroded Mg alloy surface into an anti-corrosion coating in excited CO2

Abstract: Despite their energy-efficient merits as promising light-weight structural materials, magnesium (Mg) based alloys suffer from inadequate corrosion resistance. One primary reason is that the native surface film on Mg formed in air mainly consists of Mg(OH)2 and MgO, which is porous and unprotective, especially in humid environments. Here, we demonstrate an environmentally benign method to grow a protective film on the surface of Mg/Mg alloy samples at room temperature, via a direct reaction of already-existing surface film with excited CO2. Moreover, for samples that have been corroded obviously on surface, the corrosion products can be converted directly to create a new protective surface. Mechanical tests show that compared with untreated samples, the protective layer can elevate the yield stress, suppress plastic instability and prolong compressive strains without peeling off from the metal surface. This environmentally friendly surface treatment method is promising to protect Mg alloys, including those already-corroded on the surface.

Trends in therapeutic and prevention strategies for management of Bovine Mastitis: An overview

Abstract: Mastitis is one of the most economically significant diseases for the dairy industry for backyard farmers in developing countries and high producing herds worldwide. Two of the major factors impeding reduction in the incidence of this disease is [a] the lack of availability of an effective vaccine capable of protecting against multiple etiological agents and [b] propensity of some of the etiological agents to develop persistent antibiotic resistance in biofilms. This is further complicated by the continuing revolving shift in the predominant etiological agents of mastitis, depending upon a multitude of factors such as variability in hygienic practices on farms, easy access leading to overuse of appropriate or inappropriate antibiotics at suboptimal concentrations, particularly in developing countries, and lack of compliance with the recommended treatment schedules. Regardless, Staphylococcus aureus and Streptococcus uberis followed by Escherichia coli, Streptococcus agalactiae has become the predominant etiological agents of bovine mastitis followed Streptococcus agalactiae, Streptococcus dysagalactiae, Klebsiella pneumonia and the newly emerging Mycoplasma bovis. Current approaches being pursued to reduce the negative economic impact of this disease are through early diagnosis of infection, immediate treatment with an antibiotic found to either inhibit or kill the pathogen(s) in vitro using planktonic cultures and the use of the currently marketed vaccines regardless of their demonstrated effectiveness. Given the limitations of breeding programs, including genetic selection to improve resistance against infectious diseases including mastitis, it is imperative to have the availability of an effective broad-spectrum, preferably cross-protective, vaccine capable of protecting against bovine mastitis for reduction in the incidence of bovine mastitis, as well as interrupting the potential cross-species transmission to humans. This overview highlights the major etiological agents, factors affecting susceptibility to mastitis, and the current status of antibiotic-based therapies and prototype vaccine candidates or commercially available vaccines against bovine mastitis as potential preventative strategies. © 2013 Tiwari JG, et al.

2013 Atomic spectrometry update—A review of advances in X-ray fluorescence spectrometry

Abstract: This review comments on the ever expanding range of work using the XRF group of techniques published approximately between April 2012 and March 2013. It presents innovative work as opposed to the wealth of contributions that combine XRF spectrometry in conjunction with other analytical techniques and those descriptions of the valuable routine applications published during the review period. New specialised laboratory instruments, X-ray sources and data processing procedures have been introduced as well as further detector development. Portable and hand-held systems have been increasingly used and the literature represents the widening application of μ-SR techniques for XRF mapping and insights of the sub-cellular metabolisms of animals and plants. Applications using TXRF were published dealing with samples from the pharmaceutical industry, biological tissues, extraterrestrial samples and the analysis of nuclear fuels. Nano-particles feature in many applications and this review is enlivened by reports on more space missions. Climate change, environmental studies and green chemistry feature along with work on archaeological and cultural heritage samples including the authentication of an eighteenth century harpsichord varnish.