Pub Date : 2016-01-17DOI: 10.26713/JAMCNP.V3I1.344
A. Wajid, S. Jabeen
Fine structure energy levels, transition probabilities and oscillator strength for terms belonging to the ground configuration, (rm 4s^{2}4p^{2}) and the first exited odd parity configurations (rm 4s4p^{3}), (rm 4s^24p5s) and (rm 4s^{2}4p4d) of Ge-I like ions have been calculated using Hartree-Fock method with relativistic correction incorporating large number of interacting configurations (rm[4s^{2}4p(4f+5p+5g), 4s4p^{2}(4d+5s), 4p^{3}(4d+5s)]). Experimentally reported levels have been compared with theoretical results establishing energy parameters in the first eleven members of the sequence (Ge I-Mo XI). The configuration (rm 4s^{2}4p4d) in Rb VI, Sr VII, and (rm 4s4p^3) except (rm 4s4p^{3}) (rm^{5}S_2) level in Ge-I, are not observed yet. A systematic study of Slater parameters in the isoelectronic sequence enabled us to make precise predictions of the missing energy levels belonging to these configurations.
{"title":"Study of Lowest Odd Parity Configurations in Ge-I Like Ions","authors":"A. Wajid, S. Jabeen","doi":"10.26713/JAMCNP.V3I1.344","DOIUrl":"https://doi.org/10.26713/JAMCNP.V3I1.344","url":null,"abstract":"Fine structure energy levels, transition probabilities and oscillator strength for terms belonging to the ground configuration, (rm 4s^{2}4p^{2}) and the first exited odd parity configurations (rm 4s4p^{3}), (rm 4s^24p5s) and (rm 4s^{2}4p4d) of Ge-I like ions have been calculated using Hartree-Fock method with relativistic correction incorporating large number of interacting configurations (rm[4s^{2}4p(4f+5p+5g), 4s4p^{2}(4d+5s), 4p^{3}(4d+5s)]). Experimentally reported levels have been compared with theoretical results establishing energy parameters in the first eleven members of the sequence (Ge I-Mo XI). The configuration (rm 4s^{2}4p4d) in Rb VI, Sr VII, and (rm 4s4p^3) except (rm 4s4p^{3}) (rm^{5}S_2) level in Ge-I, are not observed yet. A systematic study of Slater parameters in the isoelectronic sequence enabled us to make precise predictions of the missing energy levels belonging to these configurations.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133629594","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-29DOI: 10.26713/JAMCNP.V2I3.358
P. Srivastava, S. Dhar, N. Jaiswal
The electronic and transport properties of both zigzag graphene nanoribbons (ZGNRs) and armchair graphene nanoribbons (AGNRs) doped with coinage metals (CM) Cu, Au and Ag has been investigated by employing ab-initio approach using non equilibrium Green’s function combined with density functional theory. In Cu-doped ZGNRs, it is observed that the linear positive bias I–V curve and conductance is higher due to doping towards the centre of the ribbon. Doping at strategic positions yield currents such that the semiconductor to metal transition takes place in all the Cu-doped AGNRs. Au-doped ZGNRs exhibit stable structure and semimetallic nature is predicted with a high DOS peak distributed over a narrow energy region at the Fermi level. Our calculations for the magnetic properties predict that Au functionalization leads to semiconducting nature with different band gaps for spin up and spin down. Au-doped AGNRs are semiconducting with lower total energy for the FM configuration, and the I-V characteristics reveal semiconductor to metal transition. The spin injection is voltage controlled in all the investigated Au-doped AGNRs. The transmission spectrum (T.S) of Ag-doped ZGNRs present heightened electronic activity due to interaction between Ag impurities and edge states of the ZGNRs. Significant transport properties applicable for various device applications at the nano-regime are thus reported in all the coinage metal doped GNRs.
{"title":"AB Initio Study of Coinage Metal Doped Graphene Nano Ribbons","authors":"P. Srivastava, S. Dhar, N. Jaiswal","doi":"10.26713/JAMCNP.V2I3.358","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.358","url":null,"abstract":"The electronic and transport properties of both zigzag graphene nanoribbons (ZGNRs) and armchair graphene nanoribbons (AGNRs) doped with coinage metals (CM) Cu, Au and Ag has been investigated by employing ab-initio approach using non equilibrium Green’s function combined with density functional theory. In Cu-doped ZGNRs, it is observed that the linear positive bias I–V curve and conductance is higher due to doping towards the centre of the ribbon. Doping at strategic positions yield currents such that the semiconductor to metal transition takes place in all the Cu-doped AGNRs. Au-doped ZGNRs exhibit stable structure and semimetallic nature is predicted with a high DOS peak distributed over a narrow energy region at the Fermi level. Our calculations for the magnetic properties predict that Au functionalization leads to semiconducting nature with different band gaps for spin up and spin down. Au-doped AGNRs are semiconducting with lower total energy for the FM configuration, and the I-V characteristics reveal semiconductor to metal transition. The spin injection is voltage controlled in all the investigated Au-doped AGNRs. The transmission spectrum (T.S) of Ag-doped ZGNRs present heightened electronic activity due to interaction between Ag impurities and edge states of the ZGNRs. Significant transport properties applicable for various device applications at the nano-regime are thus reported in all the coinage metal doped GNRs.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132877398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-29DOI: 10.26713/JAMCNP.V2I3.387
P. Malik, Suresh C. Sharma, Rinku Sharma
The excitation of terahertz (THz) surface plasmons by a density modulated relativistic electron beam propagating in a parallel plane semiconducting structure is investigated. The interaction of the electromagnetic surface wave with density modulated electron beam in the guiding structure is examined in the present work, which shows a significant enhancement in the radiation wave. The growth rate of the instability increases linearly with modulation index and reaches the largest value when the phase matching condition is satisfied in the generation of THz radiation wave, i.e., when the phase velocity of the THz radiation wave is comparable to the velocity of modulated beam. In addition, the growth rate of instability scales as one-third power of beam current and modulation index. Moreover,the surface plasmons resonance can be tuned in THz frequency range by the conventional doping concentration of the semiconductors.
{"title":"Effect on THz Surface Plasmons of A Density Modulated Relativistic Electron Beam in A Parallel Plane Semiconducting Structure","authors":"P. Malik, Suresh C. Sharma, Rinku Sharma","doi":"10.26713/JAMCNP.V2I3.387","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.387","url":null,"abstract":"The excitation of terahertz (THz) surface plasmons by a density modulated relativistic electron beam propagating in a parallel plane semiconducting structure is investigated. The interaction of the electromagnetic surface wave with density modulated electron beam in the guiding structure is examined in the present work, which shows a significant enhancement in the radiation wave. The growth rate of the instability increases linearly with modulation index and reaches the largest value when the phase matching condition is satisfied in the generation of THz radiation wave, i.e., when the phase velocity of the THz radiation wave is comparable to the velocity of modulated beam. In addition, the growth rate of instability scales as one-third power of beam current and modulation index. Moreover,the surface plasmons resonance can be tuned in THz frequency range by the conventional doping concentration of the semiconductors.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"1614 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123372685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.346
S. R. Bongu, P. Bisht, T. V. Thu, A. Sandhu
Multiple nonlinear optical (NLO) responses of gold nanoparticles-grafted reduced graphene oxide (Au-rGO) nanocomposite have been studied with open aperture Z-scan setup. The nanocomposite shows the effect of saturable absorption (SA) at lower intensity that flips to reverse saturable absorption (RSA) on increasing the input irradiance. The results have been explained on the basis of the Pauli-blocking and multiphoton absorption. The NLO response of the material has been compared with the electronic diode characteristics. The simulations of the NLO responses of the nanocomposite have been done by varying saturation intensity and two-photon absorption coefficient of the material.
{"title":"Multiple Nonlinear Optical Response of Gold Decorated-Reduced Graphene Oxide-Nanocomposite for Photonic Applications","authors":"S. R. Bongu, P. Bisht, T. V. Thu, A. Sandhu","doi":"10.26713/JAMCNP.V2I3.346","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.346","url":null,"abstract":"Multiple nonlinear optical (NLO) responses of gold nanoparticles-grafted reduced graphene oxide (Au-rGO) nanocomposite have been studied with open aperture Z-scan setup. The nanocomposite shows the effect of saturable absorption (SA) at lower intensity that flips to reverse saturable absorption (RSA) on increasing the input irradiance. The results have been explained on the basis of the Pauli-blocking and multiphoton absorption. The NLO response of the material has been compared with the electronic diode characteristics. The simulations of the NLO responses of the nanocomposite have been done by varying saturation intensity and two-photon absorption coefficient of the material.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130319968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.339
Haroon, M. Ahsan
Using exact diagonalization, we study double quantum dot system with one of the dots attached to the ideal leads acting as source and drain in T-shaped geometry. The leads are incorporated in zero-bandwidth limit by replacing their band structures with one level coinciding with Fermi levels in the respective leads. For the half-filled case, the spin-spin correlation for the dots are calculated numerically at zero as well as finite temperatures. At zero temperature, an antiferromagnetic correlation between the dots is observed for finite values of interdot tunneling matrix-element. The antiferromagnetic correlation between the dots changes remarkably for large values of ondot Coulomb interaction both at zero as well as finite temperatures. The spin-spin correlation between the dots is significantly reduced even for small values of the inderdot Coulomb interaction compared to the ondot Coulomb interaction. At a small value of temperature, the spin-spin correlation between the dots exhibits a (negative) maximum due to contributions coming from thermal excitations to low-lying states.
{"title":"Exact Diagonalization Study of Double Quantum Dot System in Zero-bandwidth Limit","authors":"Haroon, M. Ahsan","doi":"10.26713/JAMCNP.V2I3.339","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.339","url":null,"abstract":"Using exact diagonalization, we study double quantum dot system with one of the dots attached to the ideal leads acting as source and drain in T-shaped geometry. The leads are incorporated in zero-bandwidth limit by replacing their band structures with one level coinciding with Fermi levels in the respective leads. For the half-filled case, the spin-spin correlation for the dots are calculated numerically at zero as well as finite temperatures. At zero temperature, an antiferromagnetic correlation between the dots is observed for finite values of interdot tunneling matrix-element. The antiferromagnetic correlation between the dots changes remarkably for large values of ondot Coulomb interaction both at zero as well as finite temperatures. The spin-spin correlation between the dots is significantly reduced even for small values of the inderdot Coulomb interaction compared to the ondot Coulomb interaction. At a small value of temperature, the spin-spin correlation between the dots exhibits a (negative) maximum due to contributions coming from thermal excitations to low-lying states.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131368457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.348
N. Gupta, A. Tewari, Suresh C. Sharma
The role of plasma parameters (electron density and temperature, ion density and temperature) on the growth and field emission properties of two dimensional graphene sheet has been theoretically investigated. A theoretical model of charge neutrality, including the kinetics of electrons, negatively and positively charged ions, neutral atoms and the energy balance of various species has been developed. Numerical calculations of the graphene for different plasma parameters (electron density and temperature, ion density and temperature) have been carried out for the typical glow discharge plasma parameters. It is found that the thickness of graphene sheet decreases with plasma parameters and hence the field emission of electrons from the graphene sheet increases. Some of our theoretical results are in compliance with the existing experimental observations.
{"title":"Role of Plasma Parameters on the Growth and Field Emission Properties of 2D Graphene Sheet","authors":"N. Gupta, A. Tewari, Suresh C. Sharma","doi":"10.26713/JAMCNP.V2I3.348","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.348","url":null,"abstract":"The role of plasma parameters (electron density and temperature, ion density and temperature) on the growth and field emission properties of two dimensional graphene sheet has been theoretically investigated. A theoretical model of charge neutrality, including the kinetics of electrons, negatively and positively charged ions, neutral atoms and the energy balance of various species has been developed. Numerical calculations of the graphene for different plasma parameters (electron density and temperature, ion density and temperature) have been carried out for the typical glow discharge plasma parameters. It is found that the thickness of graphene sheet decreases with plasma parameters and hence the field emission of electrons from the graphene sheet increases. Some of our theoretical results are in compliance with the existing experimental observations.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"32 11","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114035396","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.349
A. Shastri, A. Mandal, Param Singh, B. Jagatap
The vacuum ultraviolet (VUV) photoabsorption spectra of the dihalomethanes (rm CH_2X_2 (X=Cl, Br, I)) are studied using synchrotron radiation in the energy region 6–11.8 eV ((sim)49,000–95,200 cm(^{−1})). A detailed comparison is made to identify similarities, differences and trends in the spectra and excited state structure of these three molecules. The electronic spectra of the dihalomethanes in this region are dominated by Rydberg series of (ns), (np) and (nd) type. Quantum defect analysis reveals that the Rydberg series in all the dihalomethanes originate from the four outermost halogen lone pair non-bonding orbitals. On going from Cl to I, the energy difference between the first four ionization potentials decreases which as a consequence leads to spectral congestion and complications in spectral assignments. In all three molecules, several Rydberg transitions are accompanied by vibrational structure. A notable common feature seen in the vibronic structure is the excitation of the (nu_3) ((rm C)(rm -)(rm X) symmetric stretch) mode to form extensive progressions. Additionally, the (nu_1) ((rm C)(rm -)(rm H) symmetric stretch), (nu_2) ((rm CH_2) bend) and (nu_8) ((rm CH_2) wag) modes are observed in (rm CH_2Cl_2) and (rm CH_2I_2), although they do not form long progressions. Quantum chemical calculations of ground and excited states are used to support the analysis and an improved theory-experiment comparison is provided for (rm CH_2Br_2).
{"title":"Electronic Excited States of the Dihalomethanes, (rm CH_2X_2 (X=Cl, Br, I))","authors":"A. Shastri, A. Mandal, Param Singh, B. Jagatap","doi":"10.26713/JAMCNP.V2I3.349","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.349","url":null,"abstract":"The vacuum ultraviolet (VUV) photoabsorption spectra of the dihalomethanes (rm CH_2X_2 (X=Cl, Br, I)) are studied using synchrotron radiation in the energy region 6–11.8 eV ((sim)49,000–95,200 cm(^{−1})). A detailed comparison is made to identify similarities, differences and trends in the spectra and excited state structure of these three molecules. The electronic spectra of the dihalomethanes in this region are dominated by Rydberg series of (ns), (np) and (nd) type. Quantum defect analysis reveals that the Rydberg series in all the dihalomethanes originate from the four outermost halogen lone pair non-bonding orbitals. On going from Cl to I, the energy difference between the first four ionization potentials decreases which as a consequence leads to spectral congestion and complications in spectral assignments. In all three molecules, several Rydberg transitions are accompanied by vibrational structure. A notable common feature seen in the vibronic structure is the excitation of the (nu_3) ((rm C)(rm -)(rm X) symmetric stretch) mode to form extensive progressions. Additionally, the (nu_1) ((rm C)(rm -)(rm H) symmetric stretch), (nu_2) ((rm CH_2) bend) and (nu_8) ((rm CH_2) wag) modes are observed in (rm CH_2Cl_2) and (rm CH_2I_2), although they do not form long progressions. Quantum chemical calculations of ground and excited states are used to support the analysis and an improved theory-experiment comparison is provided for (rm CH_2Br_2).","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127424085","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.342
Suresh C. Sharma, A. Tewari, Ravi Gupta
Carbon nanotubes (CNTs) are currently attractive materials for a diverse range of applications because of their extra ordinary mechanical and electrical properties. Their application has already been demonstrated in field emission displays, nanoscale electronic devices, biosensors and hydrogen storage medium. The field emission properties of carbon nanotubes are an important field of study because they give very high values of current density as compared to the already existing field emission devices. The effect of various factors such as plasma parameters, substitutional atoms, dimensional effects, anode-cathode distance etc. on field emission from CNT has also been extensively studied. The present talk will cover the plasma production and effect of doping of hetero-atoms on the growth and field emission properties of Carbon Nanotubes (CNTs) tip placed over a cylindrical surface in complex plasma. A theoretical model incorporating kinetics of plasma species such as electron, ions and neutral atoms including doping elements like nitrogen (N), Boron (B), Potassium (K), Cesium (Cs) and energy balance of CNTs in complex plasma has been developed. The effect of doping elements of N, B, K, and Cs on the growth of CNTs namely the tip radius has been carried out for typical glow discharge plasma parameters. It is found that doping elements affect the radius of CNTs extensively. We obtained small radii for CNT doped with N and large radius for CNT doped with B. The field emission characteristics from CNTs have therefore been suggested on the basis of results obtained. Some of theoretical results are in compliance with the existing experimental observations.
{"title":"Role of Plasma and Doping Elements on the Growth and Field Emission Properties of Metallic Carbon Nanotube (CNT) Tip Placed over Cylindrical Surface","authors":"Suresh C. Sharma, A. Tewari, Ravi Gupta","doi":"10.26713/JAMCNP.V2I3.342","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.342","url":null,"abstract":"Carbon nanotubes (CNTs) are currently attractive materials for a diverse range of applications because of their extra ordinary mechanical and electrical properties. Their application has already been demonstrated in field emission displays, nanoscale electronic devices, biosensors and hydrogen storage medium. The field emission properties of carbon nanotubes are an important field of study because they give very high values of current density as compared to the already existing field emission devices. The effect of various factors such as plasma parameters, substitutional atoms, dimensional effects, anode-cathode distance etc. on field emission from CNT has also been extensively studied. The present talk will cover the plasma production and effect of doping of hetero-atoms on the growth and field emission properties of Carbon Nanotubes (CNTs) tip placed over a cylindrical surface in complex plasma. A theoretical model incorporating kinetics of plasma species such as electron, ions and neutral atoms including doping elements like nitrogen (N), Boron (B), Potassium (K), Cesium (Cs) and energy balance of CNTs in complex plasma has been developed. The effect of doping elements of N, B, K, and Cs on the growth of CNTs namely the tip radius has been carried out for typical glow discharge plasma parameters. It is found that doping elements affect the radius of CNTs extensively. We obtained small radii for CNT doped with N and large radius for CNT doped with B. The field emission characteristics from CNTs have therefore been suggested on the basis of results obtained. Some of theoretical results are in compliance with the existing experimental observations.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128445151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.338
Rangappa Santosh, S. Ghosal
Molecular hydrogen and its isotope HD acted as one of the most important interstellar coolants in the primordial gas medium. In this paper, we present accurate time-independent quantum mechanical (TIQM) rate coefficients of formation of ultracold HD molecules by ({rm D} +{rm H}_2(v,j)to {rm HD}(v', j')+{rm H}) reaction at very low collision energy. State resolved integral cross sections between different rotational ((j)) and vibrational ((v)) levels and corresponding Boltzmann-averaged thermal rate coefficients are computed between temperature (rm T = 10^{-8}K)-(rm 10K). We found the exponential decrease of the rate coefficients with reducing temperature following Arrhenius' empirical equation is not valid at ultracold temperature limit. At lower temperatures, the rate coefficients become independent of temperature (constant) and Wigner's threshold laws are obeyed. Since cooling of the primordial gases lead to the formation of the first structures of the universe, inclusion of the accurate low-temperature rate coefficients will lead to improved modeling for the evolution of the early universe.
{"title":"Quantum Mechanical Rate Coefficient of Formation of HD Molecule at Ultracold Temperatures: Its Importance in Interstellar Cooling","authors":"Rangappa Santosh, S. Ghosal","doi":"10.26713/JAMCNP.V2I3.338","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.338","url":null,"abstract":"Molecular hydrogen and its isotope HD acted as one of the most important interstellar coolants in the primordial gas medium. In this paper, we present accurate time-independent quantum mechanical (TIQM) rate coefficients of formation of ultracold HD molecules by ({rm D} +{rm H}_2(v,j)to {rm HD}(v', j')+{rm H}) reaction at very low collision energy. State resolved integral cross sections between different rotational ((j)) and vibrational ((v)) levels and corresponding Boltzmann-averaged thermal rate coefficients are computed between temperature (rm T = 10^{-8}K)-(rm 10K). We found the exponential decrease of the rate coefficients with reducing temperature following Arrhenius' empirical equation is not valid at ultracold temperature limit. At lower temperatures, the rate coefficients become independent of temperature (constant) and Wigner's threshold laws are obeyed. Since cooling of the primordial gases lead to the formation of the first structures of the universe, inclusion of the accurate low-temperature rate coefficients will lead to improved modeling for the evolution of the early universe.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"97 ","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133523515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-28DOI: 10.26713/JAMCNP.V2I3.337
J. Panwar, Suresh C. Sharma, Rinku Sharma
We develop an analytical formalism for tunable coherent terahertz (THz) radiation generation from bunched relativistic electron beam (REB) counter -propagating to the surface wave in the vacuum region Compton backscatters the surface wave. Plasma supports the surface wave that acquires a large wave number around pump wave frequency. The surface wave extends into vacuum region that can be employed as a wiggler for the generation of terahertz radiation. As the beam bunches pass through the surface plasma wave wiggler, they acquire a transverse velocity, constituting a transverse current producing coherent THz radiation. It was found that the terahertz power increases with electric field as well as with the thermal velocity of electrons. It was also found that the growth rate and efficiency of the instability both increases with the modulation index of the density modulated beam.
{"title":"Terahertz Radiation Emission from A Surface Wave Pumped Free Electron Laser","authors":"J. Panwar, Suresh C. Sharma, Rinku Sharma","doi":"10.26713/JAMCNP.V2I3.337","DOIUrl":"https://doi.org/10.26713/JAMCNP.V2I3.337","url":null,"abstract":"We develop an analytical formalism for tunable coherent terahertz (THz) radiation generation from bunched relativistic electron beam (REB) counter -propagating to the surface wave in the vacuum region Compton backscatters the surface wave. Plasma supports the surface wave that acquires a large wave number around pump wave frequency. The surface wave extends into vacuum region that can be employed as a wiggler for the generation of terahertz radiation. As the beam bunches pass through the surface plasma wave wiggler, they acquire a transverse velocity, constituting a transverse current producing coherent THz radiation. It was found that the terahertz power increases with electric field as well as with the thermal velocity of electrons. It was also found that the growth rate and efficiency of the instability both increases with the modulation index of the density modulated beam.","PeriodicalId":239838,"journal":{"name":"Journal of Atomic, Molecular, Condensate and Nano Physics","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129443409","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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