Ionization of the hydrogen molecular ion under linearly polarized intense laser fields is simulated by direct solution of the fixed-nuclei time-dependent Schrödinger equation for λ = 790 nm and I = 1 × 1014 W cm−2. Different adaptive grids used in this study produced very similar results. The results are in agreement with, and thus support, the results of recent calculations carried out by other researchers. Detailed structure of the ionization rates is presented which has not been reported so far in the literature. The use of the virtual detector method resulted in more details of the ionization rates of the hydrogen ion molecule and hydrogen atom. This method especially allowed a simultaneous detection of the parallel and perpendicular components of the ionization rates.
A new simulation box setup is introduced for the precise description of the wavepacket evolution of two electronic systems in intense laser pulses. In this box, the regions of the hydrogen molecule H(2), and singly and doubly ionized species, H(2) (+) and H(2) (+2), are well discernible and their time-dependent populations are calculated at different laser field intensities. In addition, some new regions are introduced and characterized as quasi-double ionization and their time-dependencies on the laser field intensity are calculated and analyzed. The adopted simulation box setup is special in that it assures proper evaluation of the second ionization. In this study, the dynamics of the electrons and nuclei of the hydrogen molecule are separated based on the adiabatic approximation. The time-dependent Schrödinger and Newton equations are solved simultaneously for the electrons and the nuclei, respectively. Laser pulses of 390 nm wavelength at four different intensities (i.e., 1 × 10(14), 5 × 10(14), 1 × 10(15), and 5 × 10(15) W cm(-2)) are used in these simulations. Details of the central H(2) region are also presented and discussed. This region is divided into four sub-regions related to the ionic state H(+)H(-) and covalent (natural) state HH. The effect of the motion of nuclei on the enhanced ionization is discussed. Finally, some different time-dependent properties are calculated, their dependencies on the intensity of the laser pulse are studied, and their correlations with the populations of different regions are analyzed.
Component of the instantaneous ionization rate (IIR) is introduced and calculated for H
Exploring highly active, stable, and inexpensive electrocatalysts for the oxygen reduction reaction (ORR) is pivotal in developing high-performance energy conversion devices. Moreover, the production of catalysts containing transition metals with the appropriate nitrogen doping level is a potential approach to increase ORR catalytic efficiency, especially under acidic conditions. In this study, a hierarchical graphitic porous carbon-containing Fe and N was obtained via pyrolysis of a bimetal MOF (Fe/ZIF-8) composited with pyrrole. Further experimental and theoretical results confirmed that the synergistic effects between Fe-based nanoparticles and N-doping in the networks are likely form one of the main reasons for better ORR performance. Under optimized conditions, the resultant Fe-bNCNT/NC-900 (iron-based nanoparticles enwrapped in bamboo-like nitrogen-doped carbon nanotubes (bNCNTs) grown on N-doped sheet-like carbon) exhibits high electrocatalytic activity, high selectivity (direct 4e– reduction of oxygen to water), and stability in both acidic and alkaline electrolytes. Under acidic conditions, the half-wave potential (E 1/2 = 0.770 VRHE) of Fe-bNCNT/NC-900 is comparable to commercial Pt/C (E 1/2 = 0.800 VRHE). However, this catalyst shows better activity with a half-wave potential of 0.920 VRHE, which is more than Pt/C (E 1/2 = 0.880 VRHE) in an alkaline electrolyte. The E 1/2 of Fe-bNCNT/NC-900 under acidic and alkaline conditions experienced a 170 and 28 mV loss after 20 000 continuous cycles, and these results show the prepared catalyst has promising stability.
In the first part of this paper, the different distinguishable pathways and regions of the single and sequential double ionization are determined and discussed. It is shown that there are two distinguishable pathways for the single ionization and four distinct pathways for the sequential double ionization. It is also shown that there are two and three different regions of space which are related to the single and double ionization respectively. In the second part of the paper, the time dependent Schrödinger and Newton equations are solved simultaneously for the electrons and the nuclei of H 2 respectively. The electrons and nuclei dynamics are separated on the base of the adiabatic approximation. The soft-core potential is used to model the electrostatic interaction between the electrons and the nuclei. A variety of wavelengths (390 nm, 532 nm and 780 nm) and intensities ( 5 × 10 14 W cm −2 and 5 × 10 15 W cm −2 ) of the ultrashort intense laser pulses with a sinus second order envelope function are used. The behaviour of the time dependent classical nuclear dynamics in the absence and present of the laser field are investigated and compared. In the absence of the laser eld, there are three distinct sections for the nuclear dynamics on the electronic ground state energy curve. The bond hardening phenomenon does not appear in this classical nuclear dynamics simulation.
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