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Effects of inner electrons on atomic strong-field ionization dynamics  [PDF]
J. Rapp,D. Bauer
Physics , 2013, DOI: 10.1103/PhysRevA.89.033401
Abstract: The influence of inner electrons on the ionization dynamics in strong laser fields is investigated in a wavelength regime where the inner electron dynamics is usually assumed to be negligible. The role of inner electrons is of particular interest for the application of frozen-core approximations and pseudopotentials in time-dependent density functional theory (TDDFT) and the single-active-electron (SAE) approximation in strong-field laser physics. Results of TDDFT and SAE calculations are compared with exact ones obtained by the numerical ab initio solution of the three-electron time-dependent Schr\"odinger equation for a lithium model atom. It is found that dynamical anti-screening, i.e., a particular form of dynamical core polarization, may substantially alter the ionization rate in the single-photon regime. Requirements for the validity of the approximations in the single and multiphoton ionization domain are identified.
Dynamic core polarization in strong-field ionization of CO molecules  [PDF]
Bin Zhang,Jianmin Yuan,Zengxiu Zhao
Physics , 2013, DOI: 10.1103/PhysRevLett.111.163001
Abstract: The orientation-dependent strong-field ionization of CO molecules is investigated using the fully propagated three-dimensional time-dependent Hartree-Fock theory. The full ionization results are in good agreement with recent experiments. The comparisons between the full method and single active orbital (SAO) method show that although the core electrons are generally more tightly bounded and contribute little to the total ionization yields, their dynamics cannot be ignored, which effectively modify the behaviors of electrons in the highest occupied molecular orbital. By incorporating it into the SAO method, we identify that the dynamic core polarization plays an important role in the strong-field tunneling ionization of CO molecules, which is helpful for future development of tunneling ionization theory of molecules beyond single active electron approximation.
Strong variable linear polarization in the cool active star II Peg  [PDF]
L. Rosén,O. Kochukhov,G. A. Wade
Physics , 2013, DOI: 10.1093/mnrasl/slt102
Abstract: Magnetic fields of cool active stars are currently studied polarimetrically using only circular polarization observations. Including linear polarization in the reconstruction of stellar magnetic fields allows more information about the magnetic field to be extracted and significantly improves the reliability of stellar magnetic field maps. The goal of this study is to initiate systematic observations of active stars in all four Stokes parameters and to identify cool stars for which linear polarization can be detected at a level sufficient for Zeeman Doppler imaging (ZDI). Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and sigma Gem, were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope during a time period from February 2012 to January 2013. The least-squares deconvolution procedure was applied to derive mean polarization profiles of all four Stokes parameters. Linear polarization was detected in all four stars in at least one observation. At the same time, II Peg showed an exceptionally strong and highly variable linear polarization signature throughout all observations. This establishes II Peg as the first promising target for ZDI in all four Stokes parameters and suggests the feasibility of such an analysis with existing equipment for at least a few of the most active cool stars.
Dynamical symmetry breaking under core excitation in graphite: Polarization correlation in soft X-ray recombination emission  [PDF]
Y. Harada,T. Tokushima,Y. Takata,T. Takeuchi,Y. Kitajima,S. Tanaka,Y. Kayanuma,S. Shin
Physics , 2003, DOI: 10.1103/PhysRevLett.93.017401
Abstract: A recombination emission spectrum is applied to study the local lattice distortion due to core excitation in graphite. The recombination emission spectrum reveals a long low-energy tail when the C $1s$ electron is excited to the $\sigma^*$ core exciton state. This indicates a large local lattice distortion around the excited carbon atom within a core hole lifetime ($\sim$10fs). Theoretical calculation based upon an ionic cluster model well reproduces the experiments. The strong polarization correlation between incident and emitted X-rays is conclusive evidence of symmetry breaking in the core exciton state due to coupling with asymmetric vibrational modes.
Strong coupling constant from vacuum polarization functions in three-flavor lattice QCD with dynamical overlap fermions  [PDF]
E. Shintani,S. Aoki,H. Fukaya,S. Hashimoto,T. Kaneko,T. Onogi,N. Yamada
Physics , 2010, DOI: 10.1103/PhysRevD.89.099903
Abstract: We determine the strong coupling constant $\alpha_s$ from a lattice calculation of vacuum polarization functions (VPF) in three-flavor QCD with dynamical overlap fermions. Fitting lattice data of VPF to the continuum perturbative formula including the operator product expansion, we extract the QCD scale parameter $\Lambda_{\overline{MS}}^{(3)}$. At the $Z$ boson mass scale, we obtain $\alpha_s^{(5)}(M_Z)=0.1181(3)(^{+14}_{-12})$, where the first error is statistical and the second is our estimate of various systematic uncertainties.
Anomalous Hanle Effect in Quantum Dots : Evidence for Strong Dynamical Nuclear Polarization in Transverse Magnetic Field  [PDF]
O. Krebs,P. Maletinsky,T. Amand,B. Urbaszek,A. Lema?tre,P. Voisin,X. Marie,A. Imamoglu
Physics , 2009,
Abstract: Hanle effect is ubiquitous in the study of spin-related phenomena and has been used to determine spin lifetime, precession and transport in semiconductors. Here, we report an experimental observation of anomalous Hanle effect in individual self-assembled InAs/GaAs quantum dots where we find that a sizeable photo-created electron spin polarization can be maintained in transverse fields as high as 1T until it abruptly collapses. The striking broadening of the Hanle curve by a factor of ~20 and its bistability upon reversal of the magnetic sweep direction points to a novel dynamical nuclear spin polarization mechanism where the effective nuclear magnetic field compensates the transverse applied field. This interpretation is further supported by the measurement of actual electron Zeeman splitting which exhibits an abrupt increase at the Hanle curve collapse. Strong inhomogeneous quadrupolar interactions typical for strained quantum dots are likely to play a key role in polarizing nuclear spins perpendicular to the optically injected spin orientation.
Anisotropic spin relaxation in $n$-GaAs from strong inhomogeneous hyperfine fields produced by the dynamical polarization of nuclei  [PDF]
N. J. Harmon,T. A. Peterson,C. C. Geppert,S. J. Patel,C. J. Palmstr?m,P. A. Crowell,M. E. Flatté
Physics , 2015, DOI: 10.1103/PhysRevB.92.140201
Abstract: The hyperfine field from dynamically polarized nuclei in n-GaAs is very spatially inhomogeneous, as the nu- clear polarization process is most efficient near the randomly-distributed donors. Electrons with polarized spins traversing the bulk semiconductor will experience this inhomogeneous hyperfine field as an effective fluctuating spin precession rate, and thus the spin polarization of an electron ensemble will relax. A theory of spin relaxation based on the theory of random walks is applied to such an ensemble precessing in an oblique magnetic field, and the precise form of the (unequal) longitudinal and transverse spin relaxation analytically derived. To investigate this mechanism, electrical three-terminal Hanle measurements were performed on epitaxially grown Co$_2$MnSi/$n$-GaAs heterostructures fabricated into electrical spin injection devices. The proposed anisotropic spin relaxation mechanism is required to satisfactorily describe the Hanle lineshapes when the applied field is oriented at large oblique angles.
Importance of core polarization in halo nuclei  [PDF]
Attila Csoto
Physics , 1997,
Abstract: A comment on the importance of core polarization in halo nuclei. I point out that although core polarization is suppressed in neutron halos, it plays an essential role in their binding mechanism.
Polarization of active Janus particles  [PDF]
Thomas Bickel,Guillermo Zecua,Alois Würger
Physics , 2014, DOI: 10.1103/PhysRevE.89.050303
Abstract: We study the collective motion of Janus particles in a temperature or concentration gradient. Because of the torque exerted by an external or self-generated field, the particles align their axis on this gradient. In a swarm of self-driven particles, this polarization enhances the interactiondriven confinement. Self-polarization in a non-uniform laser beam could be used for guiding hot particles along a given trajectory.
Effects of core polarization on the nuclear Schiff moment  [PDF]
V. F. Dmitriev,R. A. Sen'kov,N. Auerbach
Physics , 2004, DOI: 10.1103/PhysRevC.71.035501
Abstract: Schiff moments were calculated for a set of nuclei with full account of core polarization effects. A finite range P and T violating weak nucleon-nucleon interaction has been used in the calculations. While in the absence of core polarization the Schiff moment depends on one combination of the weak interaction constants, in the presence of core polarization the Schiff moment depends on all three constants separately. The dominant contribution comes from isovector, $\Delta T=1$, part of the weak interaction. The effects of core polarization were found to have in general a large effect on the Schiff moments.
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