Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userThe interaction of excited atoms and few-cycle laser pulses
76
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
This work describes the first observations of the ionisation of neon in a metastable atomic state utilising a strong-field, few-cycle light pulse. We compare the observations to theoretical predictions based on the Ammosov-Delone-Krainov (ADK) theory and a solution to the time-dependent Schrodinger equation (TDSE). The TDSE provides better agreement with the experimental data than the ADK theory. We optically pump the target atomic species and demonstrate that the ionisation rate depends on the spin state of the target atoms and provide physically transparent interpretation of such a spin dependence in the frameworks of the spin-polarised Hartree-Fock and random-phase approximations.
rate research
Read More
By analyzing ``exact theoretical results from solving the time-dependent Schrodinger equation of atoms in few-cycle laser pulses, we established the general conclusion that differential elastic scattering and photo-recombination cross sections of the target ion with {em free} electrons can be extracted accurately from laser-generated high-energy electron momentum spectra and high-order harmonic spectra, respectively. Since both electron scattering and photoionization (the inverse of photo-recombination) are the conventional means for interrogating the structure of atoms and molecules, this result shows that existing few-cycle infrared lasers can be implemented for ultrafast imaging of transient molecules with temporal resolution of a few femtoseconds.
A general {it ab-initio} and non-perturbative method to solve the time-dependent Schrodinger equation (TDSE) for the interaction of a strong attosecond laser pulse with a general atom, i.e., beyond the models of quasi-one-electron or quasi-two-electron targets, is described. The field-free Hamiltonian and the dipole matrices are generated using a flexible $B$-spline $R$-matrix method. This numerical implementation enables us to construct term-dependent, non-orthogonal sets of one-electron orbitals for the bound and continuum electrons. The solution of the TDSE is propagated in time using the Arnoldi-Lanczos method, which does not require the diagonalization of any large matrices. The method is illustrated by an application to the multi-photon excitation and ionization of Ne atoms. Good agreement with $R$-matrix Floquet calculations for the generalized cross sections for two-photon ionization is achieved.
We present the first experimental data on strong-field ionization of atomic hydrogen by few-cycle laser pulses. We obtain quantitative agreement at the 10% level between the data and an {it ab initio} simulation over a wide range of laser intensities and electron energies.
Laser-plasma electron accelerators can be used to produce high-intensity X-rays, as electrons accelerated in wakefields emit radiation due to betatron oscillations.Such X-ray sources inherit the features of the electron beam; sub-femtosecond electron bunches produce betatron sources of the same duration, which in turn allow probing matter on ultrashort time scales. In this paper we show, via Particle-in-Cell simulations, that attosecond electron bunches can be obtained using low-energy, ultra-short laser beams both in the self-injection and the controlled injection regimes at low plasma densities. However, only in the controlled regime does the electron injection lead to a stable, isolated attosecond electron bunch. Such ultrashort electron bunches are shown to emit attosecond X-ray bursts with high brilliance
We investigate the carrier-envelope phase and intensity dependence of the longitudinal momentum distribution of photoelectrons resulting from above-threshold ionization of argon by few-cycle laser pulses. The intensity of the pulses with a center wavelength of 750,nm is varied in a range between $0.7 times 10^{14}$ and $unit[5.5 times 10^{14}]{W/cm^2}$. Our measurements reveal a prominent maximum in the carrier-envelope phase-dependent asymmetry at photoelectron energies of 2,$U_mathrm{P}$ ($U_mathrm{P}$ being the ponderomotive potential), that is persistent over the entire intensity range. Further local maxima are observed at 0.3 and 0.8,$U_mathrm{P}$. The experimental results are in good agreement with theoretical results obtained by solving the three-dimensional time-dependent Schr{o}dinger equation (3D TDSE). We show that for few-cycle pulses, the carrier-envelope phase-dependent asymmetry amplitude provides a reliable measure for the peak intensity on target. Moreover, the measured asymmetry amplitude exhibits an intensity-dependent interference structure at low photoelectron energy, which could be used to benchmark model potentials for complex atoms.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
