Now showing items 1-20 of 53

    • Anisotropic Hyperfine Interactions Limit the Efficiency of Spin-Exchange Optical Pumping of 3He Nuclei 

      Tscherbul, T. V.; Zhang, Peng; Sadeghpour, Hossein R.; Dalgarno, Alexander (American Physical Society (APS), 2011)
      We use accurate ab initio and quantum scattering calculations to demonstrate that the maximum He3 spin polarization that can be achieved in spin-exchange collisions with potassium (K39) and silver (Ag107) atoms is limited ...
    • Atom—Atom Collision Processes in Astrophysics: Theoretical Studies 

      Dalgarno, Alexander (American Physical Society (APS), 1967)
      Theoretical studies of atom-atom collision processes which may be relevant to the interpretation of astrophysical phenomena are reviewed. Work on excitation, ionization, and electron capture in atomic hydrogen by fast ...
    • C2absorption-line diagnostics of diffuse interstellar clouds 

      Cecchi-Pestellini, Cesare; Dalgarno, Alexander (Oxford University Press (OUP), 2002)
      The excitation of the diatomic carbon molecule in diffuse interstellar clouds is discussed for a cloud with large density fluctuations of small linear filling factor along the line of sight. Possible implications for the ...
    • Calculation of Exchange Energies Using Algebraic Perturbation Theory 

      Burrows, Brian L.; Dalgarno, Alexander; Cohen, Maurice (American Physical Society, 2010)
      An algebraic perturbation theory is presented for efficient calculations of localized states and hence of exchange energies, which are the differences between low-lying states of the valence electron of a molecule, formed ...
    • Charge exchange in collisions of beryllium with its ion 

      Zhang, Peng; Dalgarno, Alexander; Côté, Robin; Bodo, Enrico (Royal Society of Chemistry (RSC), 2011)
      Close-coupling calculations of the resonance and near resonance charge exchange in ion–atom collisions of Be+2 at low and intermediate energies are presented. Accurate ab initio calculations are carried out of the ...
    • Cold N + NH Collisions in a Magnetic Trap 

      Hummon, Matthew T.; Tscherbul, Timur V.; Klos, Jacek; Lu, Hsin-I; Tsikata, Edem; Campbell, Wesley C.; Dalgarno, Alexander; Doyle, John M. (American Physical Society, 2011)
      We present an experimental and theoretical study of atom-molecule collisions in a mixture of cold, trapped N atoms and NH molecules at a temperature of ∼600  mK. We measure a small N + NH trap loss rate coefficient of ...
    • Collision-Induced Spin Depolarization of Alkali-metal Atoms in Cold \(^3\)He Gas 

      Tscherbul, T.V.; Zhang, Peng; Sadeghpour, Hossein R.; Dalgarno, Alexander; Brahms, N.; Au, Yat Shan; Doyle, John M. (American Physical Society, 2008)
      We present a joint experimental and theoretical study of spin depolarization in collisions of alkali-metal atoms with \(^3\)He in a magnetic field. A rigorous quantum theory for spin-changing transitions is developed and ...
    • Collision-Induced Spin Exchange of Alkali-Metal Atoms With \(^3\)He: An Ab Initio Study 

      Tscherbul, T.V.; Zhang, P.; Sadeghpour, Hossein R.; Dalgarno, Alexander (American Physical Society, 2009)
      We present a rigorous quantum study of spin-exchange transitions in collisions of the alkali-metal atoms with \(^3\)He in the presence of an external magnetic field. Using accurate ab initio interaction potentials, we ...
    • Collision-induced spin exchange of alkali-metal atoms withH3e: Anab initiostudy 

      Tscherbul, T. V.; Zhang, Peng; Sadeghpour, Hossein R.; Dalgarno, Alexander (American Physical Society (APS), 2009)
      We present a rigorous quantum study of spin-exchange transitions in collisions of the alkali-metal atoms with H3e in the presence of an external magnetic field. Using accurate ab initio interaction potentials, we obtain ...
    • Collisional Properties of Cold Spin-Polarized Nitrogen Gas: Theory, Experiment, and Prospects as a Sympathetic Coolant for Trapped Atoms and Molecules 

      Tscherbul, Timur V.; Klos, Jacek; Dalgarno, Alexander; Zygelman, Bernard; Pavlovic, Zoran; Hummon, Matthew T.; Lu, Hsin-I; Tsikata, Edem; Doyle, John M. (American Physical Society, 2010)
      We report a combined experimental and theoretical study of collision-induced dipolar relaxation in a cold spin-polarized gas of atomic nitrogen (N). We use buffer gas cooling to create trapped samples of \(^{14}\)N and ...
    • Collisions of Trapped Molecules With Slow Beams 

      Tscherbul, Timur V.; Pavlovic, Zoran; Sadeghpour, Hossein R.; Côté, Robin; Dalgarno, Alexander (American Physical Society, 2010)
      We present a theoretical study of molecular-trap loss induced by collisions with slow atomic beams based on an explicit analysis of collision kinematics in the laboratory frame and a rigorous quantum description of ...
    • Comparative Analysis and Variability of the Jovian X‐Ray Spectra Detected by the Chandra and XMM‐Newton Observatories 

      Dalgarno, Alexander; Hui, Yawei; Schultz, David R.; Kharchenko, Vasili A.; Bhardwaj, Anil; Branduardi‐Raymont, Graziella; Stancil, Phillip C.; Cravens, Thomas E.; Lisse, Carey M. (American Geophysical Union, 2010)
      Expanding upon recent work, a more comprehensive spectral model based on charge exchange induced X‐ray emission by ions precipitating into the Jovian atmosphere is used to provide new understanding of the polar auroras. ...
    • Cosmological Recombination of Lithium and Its Effect on the Microwave Background Anisotropies 

      Stancil, Phillip C.; Loeb, Abraham; Zaldarriaga, Matias; Dalgarno, Alexander; Lepp, Stephen (IOP Publishing, 2002)
      The cosmological recombination history of lithium, produced during big bang nucleosynthesis, is presented using updated chemistry and cosmological parameters consistent with recent cosmic microwave background (CMB) ...
    • The dependence of nonadiabatic couplings on the origin of electron coordinates 

      Belyaev, Andrey K.; Dalgarno, Alexander; McCarroll, Ronald (AIP Publishing, 2002)
      It is shown both analytically and numerically for a number of examples that both radial and rotational nonadiabatic couplings within the standard adiabatic approach depend on the origin of the light-particle coordinates ...
    • Detection of HCO+ towards Cygnus OB2 No. 12 

      Scappini, F.; Cecchi-Pestellini, C.; Codella, C.; Dalgarno, Alexander (Oxford University Press (OUP), 2000)
      HCO+ has been detected for the first time towards the star Cygnus OB2 No. 12 through emission of the 1−0 rotational transition at 89GHz. The CO(J=2−1) transition has also been observed. The observations are consistent with ...
    • Dynamic polarizabilities of rare-earth-metal atoms and dispersion coefficients for their interaction with helium atoms 

      Chu, Xi; Dalgarno, Alexander; Groenenboom, Gerrit C. (American Physical Society (APS), 2007)
      The dynamic scalar and tensor polarizabilities of the rare-earth-metal atoms are calculated with time-dependent density functional theory. The frequency-dependent polarizabilities at imaginary frequencies are used to ...
    • Dynamics of \(OH(^{2}\Pi)–He\) Collisions in Combined Electric and Magnetic Fields 

      Tscherbul, Timur V.; Groenenboom, Gerrit C.; Krems, Roman V.; Dalgarno, Alexander (Royal Society of Chemistry, 2009)
      We use accurate quantum mechanical calculations to analyze the effects of parallel electric and magnetic fields on collision dynamics of \(OH(^{2}\Pi)\) molecules. It is demonstrated that spin relaxation in \(^{3}He–OH\) ...
    • Elastic scattering and rotational excitation of nitrogen molecules by sodium atoms 

      Loreau, Jérome; Zhang, Peng; Dalgarno, Alexander (AIP Publishing, 2011)
      A quantal study of the rotational excitation of nitrogen molecules by sodium atoms is carried out. We present the two-dimensional potential energy surface of the NaN2 complex, with the N2 molecule treated as a rigid rotor. ...
    • Energy Relaxation In Collisions Of Hydrogen And Deuterium With Oxygen Atoms 

      Zhang, Peng; Kharchenko, Vasili A.; Jamieson, M.J.; Dalgarno, Alexander (American Geophysical Union, 2009)
      Collision energy transfer processes between hydrogen, deuterium, and oxygen atoms in the upper atmospheres of the terrestrial planets are studied. A new set of interaction potentials has been constructed using an accurate ...
    • Energy Transfer in O Collisions with He Isotopes and Helium Escape from Mars 

      Bovino, S.; Zhang, Peng; Gianturco, F. A.; Dalgarno, Alexander; Kharchenko, Vasili A. (Wiley-Blackwell, 2011)
      [1] Accurate data on energy-transfer collisions between hot oxygen atoms and the atmospheric helium gas on Mars, are reported. Anisotropic cross sections for elastic collisions of O(3P) and O(1D) atoms with helium gas have ...