arXiv subjects

R. D. Glover

Publications and source records attributed to R. D. Glover.

4 recordsLinked to original sources

arXiv2021

Carrier-Envelope-Phase Dependent Strong-Field Excitation

We present a joint experimental-theoretical study on the effect of the carrier-envelope phase (CEP) of a few-cycle pulse on the atomic excitation process. We focus on the excitation rates of argon as a function of CEP in the intensity range from 50-300 TW/cm$^2$, which covers the transition between the multiphoton and tunneling regimes. Through numerical simulations based on solving the time-dependent Schrödinger equation (TDSE), we show that the resulting bound-state population is highly sensitive to both the intensity and the CEP. Because the intensity varies over the interaction region, the CEP effect is considerably reduced in the experiment. Nevertheless, the data clearly agree with the theoretical prediction, and the results encourage the use of precisely tailored laser fields to coherently control the strong-field excitation process. We find a markedly different behavior for the CEP-dependent bound-state population at low and high intensities with a clear boundary, which we attribute to the transition from the multiphoton to the tunneling regime.

physics.atom-ph↗

arXiv2019

Relativistic non-dipole effects in strong-field atomic ionization at moderate intensities

We present a detailed experimental and theoretical study on the relativistic non-dipole effects in strong-field atomic ionisation by near-infrared linearly-polarised few-cycle laser pulses in the intensity range 1014 -1015 W/cm2. We record high-resolution photoelectron momentum distributions of argon using a reaction microscope and compare our measurements with a truly ab-initio fully relativistic 3D model based on the time-dependent Dirac equation. We observe counter-intuitive peak shifts of the transverse electron momentum distribution in the direction opposite to that of laser propagation as a function of laser intensity and demonstrate an excellent agreement between experimental results and theoretical predictions.

physics.atom-ph↗

arXiv2018

Laser-based metastable krypton generation

We demonstrate the generation of metastable krypton in the long-lived 1s5 state using laser excitation. The atoms are excited through a two-photon absorption process into the 2p6 state using a pulsed optical parametric oscillator laser operating near 215 nm, after which the atoms decay quickly into the metastable state with a branching ratio of 75 %. The interaction dynamics are modeled using density matrix formalism and, by combining this with experimental observations, we are able to calculate photo-ionization and two-photon absorption cross-sections. When compared to traditional approaches to metastable production, this new approach shows great potential for high-density metastable krypton production with minimal heating of the sample. Here, we show metastable production efficiencies of up to 2% per pulse. The new experimental results gained here, when combined with the density matrix model we have developed, suggest that fractional efficiencies up to 30% are possible under optimal conditions.

physics.atom-ph↗

arXiv2016

The interaction of excited atoms and few-cycle laser pulses

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.

physics.atom-ph↗