Presence Of Homogeneous Electric Fields Research Articles

Precision-Spectroscopic Determination of the Binding Energy of a Two-Body Quantum System: The Hydrogen Atom and the Proton-Size Puzzle.

Precision measurements in Rydberg states of H with principal quantum number n in the range between 20 and 30 are reported. In the presence of homogeneous electric fields with strengths below 2 V cm^{-1}, these Rydberg states are subject to a linear Stark effect with accurately calculable Stark shifts. From the spectral positions of field-independent and field-dependent Rydberg-Stark states, we derive the n=20 and 24 Bohr energies, and the ionization energy with respect to the 2 ^{2}S_{1/2}(f=0,1) [short 2S(0,1)] metastable states. Combining these results with the 2S(1)-1S(1) transition frequency [C. G. Parthey et al., Phys. Rev. Lett. 107, 203001 (2011)PRLTAO0031-900710.1103/PhysRevLett.107.203001; A. Matveev et al., Phys. Rev. Lett. 110, 230801 (2013)PRLTAO0031-900710.1103/PhysRevLett.110.230801] and the 1S hyperfine splitting [L. Essen et al., Nature (London) 229, 110 (1971)NATUAS0028-083610.1038/229110a0], we determine the ionization frequency of the 1S(0) ground state to be 3 288 087 922 407.2(3.7)_{stat}(1.8)_{syst} kHz, which is the most precise value ever determined for the binding energy of a two-body quantum system. Using the 2S(0)-2P_{1/2}(1) interval [N. Bezginov et al., Science 365, 1007 (2019)SCIEAS0036-807510.1126/science.aau7807], we determine the Rydberg frequency to be cR_{∞}=3 289 841 960 204(15)_{stat}(7)_{syst}(13)_{2S-2P} kHz in a procedure that is insensitive to the value of the proton charge radius. These new results are discussed in the context of the proton-size puzzle.

Water co-adsorption and electric field effects on borohydride structures on Os(1 1 1) by first-principles calculations

Abstract Periodic density functional theory calculations are performed to investigate the nature of the BH 4ad and its interaction with H 2 O ad in the presence of homogenous electric field. We observed a significant charge polarity of BH 4ad on Os(1 1 1) and such property could explain the electrostatic interaction with water monomer (H ad ) with its HOH plane parallel to the surface. This interaction changes the BH ad molecular structure to BH 3ad + H ad . In the presence of homogenous electric field, the water co-adsorption effect is reduced due to the stabilization of H 2 O ad on the surface and the deviation of the O–H bond from the plane, decreasing the electrostatic interaction between BH 4ad and H 2 O ad . These fundamental findings imply accessible control of borohydride structures on an electrode surface, which could be relevant for direct borohydride fuel cell (DBFC) and reversible hydrogen storage/release applications.

Simulation study on the influence of an electric field on water evaporation

To examine the influence of an electric field on water evaporation, we carried out a water evaporation simulation in the absence and presence of homogeneous electric fields in three directions. It was found that the electric field in the direction perpendicular to the water surface enhances the water evaporation, while the electric field in the direction parallel to the water surface impedes the water evaporation. This finding qualitatively agrees with the observations in the electrospinning experiment that indicated that the application of a voltage to the tip of the syringe needle enhances the evaporation of the water droplet around the tip. We also found that the electric field in the direction from the outside of the water solution to the inside more significantly enhances the water evaporation than in the opposite direction.

Rate coefficients for resonant vibrational excitation of N 2

Rate coefficients for vibrational excitation of the nitrogen molecule, via the 2Π g shape resonance in the energy region from 0 to 5 eV have been calculated. Calculations are performed for Maxwellian electron energy distribution by using recent experimentally measured differential cross sections for excitation of the first ten vibrational levels and for elastic scattering. By using extended Monte Carlo simulations the electron energy distribution functions (EEDF) and rate coefficients are determined in non-equilibrium conditions, in a presence of homogenous electric field for typical, moderate values of the electric field over gas number density ratios, E/N. A great difference between Maxwellian and non-equilibrium rate coefficients was found due to a very specific shape of the electron energy distribution function in nitrogen under the considered conditions.

Theoretical Study of the Adsorption and Dissociation of Oxygen on Pt(111) in the Presence of Homogeneous Electric Fields

The effect of homogeneous electric fields on the adsorption energies of atomic and molecular oxygen and the dissociation activation energy of molecular oxygen on Pt(111) were studied by density functional theory (DFT). Positive electric fields, corresponding to positively charged surfaces, reduce the adsorption energies of the oxygen species on Pt(111), whereas negative fields increase the adsorption energies. The magnitude of the energy change for a given field is primarily determined by the static surface dipole moment induced by adsorption. On 10-atom Pt(111) clusters, the adsorption energy of atomic oxygen decreased by ca. 0.25 eV in the presence of a 0.51 V/A (0.01 au) electric field. This energy change, however, is heavily dependent on the number of atoms in the Pt(111) cluster, as the static dipole moment decreases with cluster size. Similar calculations with periodic slab models revealed a change in energy smaller by roughly an order of magnitude relative to the 10-atom cluster results. Calculations with adsorbed molecular oxygen and its transition state for dissociation showed similar behavior. Additionally, substrate relaxation in periodic slab models lowers the static dipole moment and, therefore, the effect of electric field on binding energy. The results presented in this paper indicate that the electrostatic effect of electric fields at fuel cell cathodes may be sufficiently large to influence the oxygen reduction reaction kinetics by increasing the activation energy for dissociation.