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1. Cosmic ray sputtering yield of interstellar ice mantles: CO and CO2 ice thickness dependence

Author

Dartois, E., Chabot, M., Barkach, T. Id, Rothard, H., Boduch, P., Augé, B., and Agnihotri, A. N.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

Cosmic-ray-induced sputtering is one of the important desorption mechanisms at work in astrophysical environments. The chemical evolution observed in high-density regions, from dense clouds to protoplanetary disks, and the release of species condensed on dust grains, is one key parameter to be taken into account in interpretations of both observations and models. This study is part of an ongoing systematic experimental determination of the parameters to consider in astrophysical cosmic ray sputtering. As was already done for water ice, we investigated the sputtering yield as a function of ice mantle thickness for the two next most abundant species of ice mantles, carbon monoxide and carbon dioxide, which were exposed to several ion beams to explore the dependence with deposited energy. These ice sputtering yields are constant for thick films. It decreases rapidly for thin ice films when reaching the impinging ion sputtering desorption depth. An ice mantle thickness dependence constraint can be implemented in the astrophysical modelling of the sputtering process, in particular close to the onset of ice mantle formation at low visual extinctions., Comment: To appear in Astronomy & Astrophysics

Published
2021
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2. Non-thermal desorption of complex organic molecules

Author

Dartois, E., Chabot, M., Barkach, T. Id, Rothard, H., Augé, B., Agnihotri, A. N., Domaracka, A., and Boduch, P.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

The occurrence of complex organic molecules (COMs) in the gas phase at low temperature in the dense phases of the ISM suggests that a non-thermal desorption mechanism is at work because otherwise, COMs should condense within a short timescale onto dust grains. Vacuum ultraviolet photodesorption has been shown to be much less efficient for complex organic molecules, such as methanol, because mostly photoproducts are ejected. The induced photolysis competes with photodesorption for large COMs, considerably lowering the efficiency to desorb intact molecules. We investigate the sputtering efficiency of complex organic molecules that are observed either in the ice mantles of interstellar dense clouds directly by infrared spectroscopy (CH3OH), or that are observed in the gas phase by millimeter telescopes (CH3COOCH3) and that could be released from interstellar grain surfaces. We irradiated ice films containing complex organic molecules (methanol and methyl acetate) and water with swift heavy ions in the electronic sputtering regime. We monitored the infrared spectra of the film as well as the species released to the gas phase with a mass spectrometer. We demonstrate that when methanol or methyl acetate is embedded in a water-ice mantle exposed to cosmic rays, a large portion is sputtered as an intact molecule, with a sputtering yield close to that of the main water-ice matrix. This must be even more true for more volatile ice matrices, such as those that are embedded in carbon monoxide. Cosmic rays penetrating deep into dense clouds provide an efficient mechanism to desorb complex organic molecules. Compared to VUV photons induced by the interaction of cosmic rays, a large portion desorb as intact molecules with a proportion corresponding to the time-dependent bulk composition of the ice mantle, the latter evolving with time as a function of fluence due to the radiolysis of the bulk., Comment: Corrected a copy/paste typo in Table 2: The CO2 stretch A value is 7.6d-17 Gerakines et al. (1995), replacing 1.8d-17 D'Hendecourt & Allamandola (1986)

Published
2019

3. Kinematics and Dynamics Analysis of 5DOF 360 Degree Machining Robot

Author

Amin, Mihir H., Bhamare, Monil M., Agnihotri, Japagna N., Patel, Dipal M., Cavas-Martínez, Francisco, Series Editor, Chaari, Fakher, Series Editor, di Mare, Francesca, Series Editor, Gherardini, Francesco, Series Editor, Haddar, Mohamed, Series Editor, Ivanov, Vitalii, Series Editor, Kwon, Young W., Series Editor, Trojanowska, Justyna, Series Editor, Chaurasiya, Prem Kumar, editor, Singh, Abhishek, editor, Verma, Tikendra Nath, editor, and Rajak, Upendra, editor

Published
2022
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4. Design Enhancement and Vibration Analysis of Bladeless Wind Turbine

Author

Agnihotri, Japagna N., Bhamare, Monil M., Amin, Mihir H., Patel, Kishan D., Subhedar, Dattatraya G., Cavas-Martínez, Francisco, Series Editor, Chaari, Fakher, Series Editor, di Mare, Francesca, Series Editor, Gherardini, Francesco, Series Editor, Haddar, Mohamed, Series Editor, Ivanov, Vitalii, Series Editor, Kwon, Young W., Series Editor, Trojanowska, Justyna, Series Editor, Kumar, Shailendra, editor, Ramkumar, J., editor, and Kyratsis, Panagiotis, editor

Published
2022
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5. Cosmic ray sputtering yield of interstellar H2O ice mantles : Ice mantle thickness dependence

Author

Dartois, E., Chabot, M., Barkach, T. Id, Rothard, H., Augé, B., Agnihotri, A. N., Domaracka, A., and Boduch, P.

Subjects
Astrophysics - Astrophysics of Galaxies
Abstract

Interstellar grain mantles present in dense interstellar clouds are in constant exchange with the gas phase via accretion and desorption mechanisms such as UV, X-ray photodesorption, cosmic ray induced sputtering, grain thermal fluctuations, and chemical reaction energy release. The relative importance of the various desorption mechanisms is of uttermost importance for astrophysical models to constrain the chemical evolution in such high density dense cloud regions. In this experimental work we investigated the sputtering yield as a function of ice mantle thickness, exposed to Xe ions at 95MeV. The ion induced ice phase transformation and the sputtering yield were simultaneously monitored by IR spectroscopy and mass spec- trometry, respectively. The sputtering yield is constant above a characteristic ice layer thickness and starts to decrease below this thickness. An estimate of the sputtering depth corresponding to this length can be evaluated. In these experiments the measured desorption depth corresponds to 30 ice layers. Assuming an effective cylindrical shape for the volume of sputtered molecules, the aspect ratio is close to unity; in the semi-infinite ice film case this ratio is the diameter to height of the cylinder. This result shows that most ejected molecules arise from a rather compact volume. The measured infinite thickness sputtering yield for water ice mantles scales as the square of the ion electronic stopping power (Se). We expect that the desorption depth dependence varies with Se^a , where a=0.5. Astrophysical models should take into account the thickness dependence constraints of these ice mantles in the interface regions when ices are close to their extinction threshold. In the very dense cloud regions, most of the water ice mantles are above this limit for the bulk of the cosmic rays., Comment: 6 pages, 5 figures

Published
2018
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7. Fragmentation Dynamics of Atomic and Molecular Clusters

Author

Méry, A., Agnihotri, A. N., Douady, J., Fléchard, X., Gervais, B., Guillous, S., Iskandar, W., Jacquet, E., Kumar, V., Matsumoto, J., Rangama, J., Ropars, F., Safvan, C. P., Shiromaru, H., Zanuttini, D., Cassimi, A., Orr, N. A., editor, Ploszajczak, M., editor, Marqués, F. M., editor, and Carbonell, J., editor

Published
2020
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12. Fragmentation Dynamics of Atomic and Molecular Clusters

Author

Méry, A., primary, Agnihotri, A. N., additional, Douady, J., additional, Fléchard, X., additional, Gervais, B., additional, Guillous, S., additional, Iskandar, W., additional, Jacquet, E., additional, Kumar, V., additional, Matsumoto, J., additional, Rangama, J., additional, Ropars, F., additional, Safvan, C. P., additional, Shiromaru, H., additional, Zanuttini, D., additional, and Cassimi, A., additional

Published
2020
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13. Unexplained dissociation pathways of two-body fragmentation of methane dication.

Author

Rajput, Jyoti, Garg, Diksha, Cassimi, A., Méry, A., Fléchard, X., Rangama, J., Guillous, S., Iskandar, W., Agnihotri, A. N., Matsumoto, J., Ahuja, R., and Safvan, C. P.

Subjects
AB-initio calculations, ION-molecule collisions, ELECTRON configuration, BRANCHING ratios, KINETIC energy
Abstract

The ion-induced fragmentation of C H 4 2 + into H+ and C H 3 + is studied using a cold target recoil ion momentum spectroscopy in coincidence with the charge state of the post-collision projectile. Using constant velocity Ar9+ and N3+, results from four different datasets are presented, with a selection on the final charge state of the projectile (Ar8+ or Ar7+ and N2+ or N+). Three distinct dissociation pathways (I, II, and III) are observed for each dataset, with the mean kinetic energy release values of around 4.7, 5.8, and 7.9 eV, respectively. The electronic states that are populated correspond to electronic configurations (1 t 2 ) − 2 and (2 a 1 ) − 1 (1 t 2 ) − 1 of the methane dication, C H 4 2 + . The relative branching ratios between the three pathways are discussed as a function of the charge state of the post-collision projectile, and a strong correlation with the specific nature of the ion–molecule interaction is found. The existing ab initio calculations have provided an explanation only for pathway II. In this article, we propose an explanation for pathway III, but pathway I still remains unexplained and requires further theoretical efforts. A discussion of the dependence of dissociation on the mode of excitation is presented. [ABSTRACT FROM AUTHOR]

Published
2022
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19. Ion induced fragmentation of diatomic molecular clusters

Author

Méry, A, primary, Agnihotri, A N, additional, Douady, J, additional, Fléchard, X, additional, Gervais, B, additional, Guillous, S, additional, Iskandar, W, additional, Jacquet, E, additional, Kumar, V, additional, Matsumoto, J, additional, Rangama, J, additional, Ropars, F, additional, Safvan, C P, additional, Shiromaru, H, additional, Zanuttini, D, additional, and Cassimi, A, additional

Published
2020
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23. Ion radiation in icy space environments: Synthesis and radioresistance of complex organic molecules

Author

Ada Bibang, Prudence C. J., primary, Agnihotri, Aditya N., additional, Augé, Basile, additional, Boduch, Philippe, additional, Desfrançois, Charles, additional, Domaracka, Alicja, additional, Lecomte, Frédéric, additional, Manil, Bruno, additional, Martinez, Rafael, additional, Muniz, Gabriel S. V., additional, Nieuwjaer, Nicolas, additional, and Rothard, Hermann, additional

Published
2019
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27. Role of a Neighbor Ion in the Fragmentation Dynamics of Covalent Molecules

Author

Méry, A., primary, Agnihotri, A. N., additional, Douady, J., additional, Fléchard, X., additional, Gervais, B., additional, Guillous, S., additional, Iskandar, W., additional, Jacquet, E., additional, Matsumoto, J., additional, Rangama, J., additional, Ropars, F., additional, Safvan, C. P., additional, Shiromaru, H., additional, Zanuttini, D., additional, and Cassimi, A., additional

Published
2017
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29. Non-thermal desorption of complex organic molecules: Efficient CH3OH and CH3COOCH3 sputtering by cosmic rays.

Author

Dartois, E., Chabot, M., Id Barkach, T., Rothard, H., Augé, B., Agnihotri, A. N., Domaracka, A., and Boduch, P.

Subjects
COSMIC rays, ICE sheets, DEUTERIUM oxide, METHYL acetate, MOLECULES, MAGNETRON sputtering
Abstract

Context. The occurrence of complex organic molecules (COMs) in the gas phase at low temperature in the dense phases of the interstellar medium suggests that a non-thermal desorption mechanism is at work because otherwise, COMs should condense within a short timescale onto dust grains. Vacuum ultraviolet (VUV) photodesorption has been shown to be much less efficient for complex organic molecules, such as methanol, because mostly photoproducts are ejected. The induced photolysis competes with photodesorption for large COMs, which considerably lowers the efficiency to desorb intact molecules. Aims. We pursue an experimental work that has already shown that water molecules, the dominant ice mantle species, can be efficiently sputtered by cosmic rays. We investigate the sputtering efficiency of complex organic molecules that are observed either in the ice mantles of interstellar dense clouds directly by infrared spectroscopy (CH3OH), or that are observed in the gas phase by millimeter telescopes (CH3COOCH3) and that could be released from interstellar grain surfaces. Methods. We irradiated ice films containing complex organic molecules (methanol and methyl acetate) and water with swift heavy ions in the electronic sputtering regime. We monitored the infrared spectra of the film as well as the species released to the gas phase with a mass spectrometer. Results. We demonstrate that when methanol or methyl acetate is embedded in a water-ice mantle exposed to cosmic rays, a large portion is sputtered as an intact molecule, with a sputtering yield close to that of the main water-ice matrix. This must be even more true for the case of more volatile ice matrices, such as those that are embedded in carbon monoxide. Conclusions. Cosmic rays penetrating deep into dense clouds provide an efficient mechanism to desorb complex organic molecules. Compared to the VUV photons, which are induced by the interaction of cosmic rays, a large portion desorb as intact molecules with a proportion corresponding to the time-dependent bulk composition of the ice mantle, the latter evolving with time as a function of fluence due to the radiolysis of the bulk. [ABSTRACT FROM AUTHOR]

Published
2019
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30. Observation of 2p3d(¹P°)→1s3d(¹Dᵉ) Radiative Transition in He-like Si, S, and Cl Ions

Author

Santos, José Paulo, Costa, A. M., Kasthurirangan, S., Saha, J. K., Agnihotri, A. N., Bhattacharyya, S., Misra, D., Kumar, A., Mukherjee, P. K., Indelicato, P., Mukherjee, T. K., and Tribedi, L. C.

Subjects
Computer Science::Performance, Physics::Fluid Dynamics, Computer Science::Networking and Internet Architecture, Physics::Accelerator Physics, Computer Science::Digital Libraries
Abstract

APS, Journals Phys. Rev. Lett., Volume 111, Issue 24

Published
2013

31. Production of Hydronium Ion (H3O)+and Protonated Water Clusters (H2O)nH+after Energetic Ion Bombardment of Water Ice in Astrophysical Environments

Author

Martinez, R., Agnihotri, A. N., Boduch, Ph., Domaracka, A., Fulvio, D., Muniz, G., Palumbo, M. E., Rothard, H., and Strazzulla, G.

Abstract

Water ice exists on many objects in space. The most abundant icy species, among them water, are present in the icy satellites of the outer Solar System giant planets. The nuclei of comets, which are mainly composed of water ice, give another example of its abundance. In the interstellar medium (ISM), ice mantles, formed by molecular species sticking on dust grains, consist mainly of water ice. All these objects are exposed to ionizing radiation like ions, UV photons, and electrons. Sputtering of atoms, molecules, ions, and radicals from icy surfaces may populate and maintain exospheres of icy objects in the Solar System. In other respects, ionized hydrides such as OH+, H2O+, and H3O+have been detected in the gas phase in star-forming regions. Interactions with cosmic rays could be an additional explanation to the current models for the formation of those species. In fact, laboratory simulations showed that the main components of the sputtered ionic species from water ice are oxygen hydrides. In this work, water ice targets were irradiated at several temperatures (10–200 K) by 90 keV O6+ions, yielding an electronic stopping power of about 12 eV/Å, when the nuclear stopping power is comparable to the electronic stopping power. Sputtering of secondary ions after bombardment of the ice target was analyzed by time-of-flight mass spectrometry (TOF-SIMS). Besides hydrogen ions (H+, H2+, H3+), also O+, O2+, OH+, (H2O)+, and clusters of (H2O)nH+with n= 1–8 are emitted. Our results show a progressive yield decrease with increasing temperature of all of the detected species. This is related to the structure of the ice: the ionic sputtering yield for crystalline ice is much lower than for an amorphous ice. For instance, amorphous ice at 10 K exhibits a yield of the order of 2 × 10–6secondary (H2O)nH+hydride ions/projectile (with n= 1–8). As the temperature is increasing toward the phase transition to crystalline ice, the yields decrease by about one order of magnitude.

Published
2019
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32. Double differential distribution of electron emission in ionization of uracil in collisions with fast bare C-ions: angular asymmetry

Author

Agnihotri, A. N., Nandi, S., Kasthurirangan, S., Kumar, A., Galassi, Mariel Elisa, Rivarola, Roberto Daniel, Champion, C., and Tribedi, L. C.

Subjects
purl.org/becyt/ford/1 [https], Física Atómica, Molecular y Química, Ciencias Físicas, IONIZATION, purl.org/becyt/ford/1.3 [https], URACIL, CARBON IONS, CIENCIAS NATURALES Y EXACTAS
Abstract

We report the energy and angular distribution of the electron emission from an RNA base molecule uracil in collisions with 3.5-MeV/u bare C ions. The absolute double differential cross sections (DDCS) are measured for emission energy between a few to 600 eV. The angular distributions are compared to those obtained for the O2 molecule in the same experiment. The single differential cross sections (SDCS) are also deduced. The energy and angular distributions of the DDCS and SDCS are compared with the state-of-the-art quantum-mechanical models based on continuum distorted wave-eikonal initial state (CDW-EIS) and correct boundary first Born (CB1) approximations which use a suitable molecular wave function for uracil. The models, however, give substantial deviations from the observed energy and angular distributions of the DDCS as well as SDCS. The CDW-EIS calculations are closer to the data compared to the CB1. In the case of uracil a large difference in the forward-backward emission of electrons was observed in comparison to that in collisions with an oxygen molecule. Fil: Agnihotri, A. N.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; India Fil: Nandi, S.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; India Fil: Kasthurirangan, S.. Institute of Chemical Technology. Department of Physics; India Fil: Kumar, A.. Bhabha Atomic Research Centre. Nuclear Physics Division; India Fil: Galassi, Mariel Elisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentina Fil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Física de Rosario (i); Argentina Fil: Champion, C.. Universite Paul Verlaine-metz. Institut de Physique, Chimie Et Materiaux. Laboratorie de Physique Moleculaire Et Des Collisions; Francia Fil: Tribedi, L. C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; India

Published
2013
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47. Ionization of RNA-uracil by highly charged carbon ions

Author

Champion, C, primary, Galassi, M E, additional, Fojón, O, additional, Lekadir, H, additional, Hanssen, J, additional, Rivarola, R D, additional, Weck, P F, additional, Agnihotri, A N, additional, Nandi, S, additional, and Tribedi, L C, additional

Published
2012
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