Non-sequential double ionization (NSDI) is a strong-field process involving the correlated emission of two electrons. This thesis proposes an analog quantum simulator to study NSDI in a helium atom, using ultracold trapped atoms to represent electrons. The core potential is replaced by an optical trap created by a laser. Rydberg atoms, with their strong long-range interactions, are ideal for simulating attosecond phenomena. A numerical simulation is conducted to observe the correlated two-electron momentum components after a laser pulse is applied.Non-sequential double ionization (NSDI) is a strong-field process involving the correlated emission of two electrons. This thesis proposes an analog quantum simulator to study NSDI in a helium atom, using ultracold trapped atoms to represent electrons. The core potential is replaced by an optical trap created by a laser. Rydberg atoms, with their strong long-range interactions, are ideal for simulating attosecond phenomena. A numerical simulation is conducted to observe the correlated two-electron momentum components after a laser pulse is applied.

Sep 5, 20240 citations

A New, Non-local Quantum Electrodynamics: Its Effect on Multiphoton Single and Double Ionization

Krishna Rai Dastidar

By considering a new, non-local quantum electrodynamics, wc have shown that the non-sequential double ionization of aloms occur due to the phase correlated two-photon excitation o f electrons.For this phase conelated excitation, two-photon rate depend.slinearly on laser intensity.However, the local nature of the radiation field gives rise to conventional multiphoton transitions, where the two-photon rate is proportional to the square of the laser intensity Wc have shown that n-photon transitions in an experiment can be modeled as a series o f these two types of transitions and hence several channels will run parallel to each other The channels for w-photon transitions are (i) a scries of phase correlated transitions giving rise to non-sequential double ionization, (ii) a senes of conventional dipole transitions giving rise to sequential ionization and (in) a mixture of phase correlated and phase non-corrclated transitions We have shown that, with the increase in laser intensity the channel comprising of only the phase correlated excitations becomes significant and gets saturated before the sequential channel can dominate, giving rise to a kink-like structure in the intensity variation of double inoi/ation 1 ins feature has been observed in the experiments on double ionization of He Wc have also provided a physical basis for the damping of non-sequcntial double inoization at the smaller wavelength, which is also an experimentally observed feature.By considering a new, non-local quantum electrodynamics, wc have shown that the non-sequential double ionization of aloms occur due to the phase correlated two-photon excitation o f electrons.For this phase conelated excitation, two-photon rate depend.slinearly on laser intensity.However, the local nature of the radiation field gives rise to conventional multiphoton transitions, where the two-photon rate is proportional to the square of the laser intensity Wc have shown that n-photon transitions in an experiment can be modeled as a series o f these two types of transitions and hence several channels will run parallel to each other The channels for w-photon transitions are (i) a scries of phase correlated transitions giving rise to non-sequential double ionization, (ii) a senes of conventional dipole transitions giving rise to sequential ionization and (in) a mixture of phase correlated and phase non-corrclated transitions We have shown that, with the increase in laser intensity the channel comprising of only the phase correlated excitations becomes significant and gets saturated before the sequential channel can dominate, giving rise to a kink-like structure in the intensity variation of double inoi/ation 1 ins feature has been observed in the experiments on double ionization of He Wc have also provided a physical basis for the damping of non-sequcntial double inoization at the smaller wavelength, which is also an experimentally observed feature.

Jan 1, 20020 citations

Multiple ionization of atoms in light field

M.R. Bedilov

Sep 1, 19970 citations

Ionization of Doubly Excited Atoms in an Electric Field

Daniel I. Khomskii

Optics and SpectroscopyMar 1, 19650 citations

Sequential double photodetachment of He− in elliptically polarized laser fields

Matthieu Génévriez, Kevin M. Dunseath, Mariko Terao-Dunseath +1 more

Four-photon double detachment of the helium negative ion is investigated experimentally and theoretically for photon energies where the transient helium atom is in the $1s2s\phantom{\rule{0.16em}{0ex}}^{3}S$ or $1s2p\phantom{\rule{0.16em}{0ex}}^{3}P^{\mathrm{o}}$ states, which subsequently ionize by absorption of three photons. Ionization is enhanced by intermediate resonances, giving rise to series of peaks in the ${\mathrm{He}}^{+}$ spectrum, which we study in detail. The ${\mathrm{He}}^{+}$ yield is measured in the wavelength ranges from 530 to 560 nm and from 685 to 730 nm and for various polarizations of the laser light. Double detachment is treated theoretically as a sequential process, within the framework of $R$ -matrix theory for the first step and effective Hamiltonian theory for the second step. Experimental conditions are accurately modeled, and the measured and simulated yields are in good qualitative and, in some cases, quantitative agreement. Resonances in the double detachment spectra can be attributed to well-defined Rydberg states of the transient atom. The double detachment yield exhibits a strong dependence on the laser polarization which can be related to the magnetic quantum number of the intermediate atomic state. We also investigate the possibility of nonsequential double detachment with a two-color experiment but observe no evidence for it.Four-photon double detachment of the helium negative ion is investigated experimentally and theoretically for photon energies where the transient helium atom is in the $1s2s\phantom{\rule{0.16em}{0ex}}^{3}S$ or $1s2p\phantom{\rule{0.16em}{0ex}}^{3}P^{\mathrm{o}}$ states, which subsequently ionize by absorption of three photons. Ionization is enhanced by intermediate resonances, giving rise to series of peaks in the ${\mathrm{He}}^{+}$ spectrum, which we study in detail. The ${\mathrm{He}}^{+}$ yield is measured in the wavelength ranges from 530 to 560 nm and from 685 to 730 nm and for various polarizations of the laser light. Double detachment is treated theoretically as a sequential process, within the framework of $R$-matrix theory for the first step and effective Hamiltonian theory for the second step. Experimental conditions are accurately modeled, and the measured and simulated yields are in good qualitative and, in some cases, quantitative agreement. Resonances in the double detachment spectra can be attributed to well-defined Rydberg states of the transient atom. The double detachment yield exhibits a strong dependence on the laser polarization which can be related to the magnetic quantum number of the intermediate atomic state. We also investigate the possibility of nonsequential double detachment with a two-color experiment but observe no evidence for it.

Physical Review AFeb 13, 20180 citations

Four-photon double detachment of the helium negative ion is investigated experimentally and theoretically for photon energies where the transient helium atom is in the

1s2s\phantom{\rule{0.16em}{0ex}}^{3}S

1s2p\phantom{\rule{0.16em}{0ex}}^{3}P^{\mathrm{o}}

states, which subsequently ionize by absorption of three photons. Ionization is enhanced by intermediate resonances, giving rise to series of peaks in the

{\mathrm{He}}^{+}

spectrum, which we study in detail. The

{\mathrm{He}}^{+}

yield is measured in the wavelength ranges from 530 to 560 nm and from 685 to 730 nm and for various polarizations of the laser light. Double detachment is treated theoretically as a sequential process, within the framework of

R

-matrix theory for the first step and effective Hamiltonian theory for the second step. Experimental conditions are accurately modeled, and the measured and simulated yields are in good qualitative and, in some cases, quantitative agreement. Resonances in the double detachment spectra can be attributed to well-defined Rydberg states of the transient atom. The double detachment yield exhibits a strong dependence on the laser polarization which can be related to the magnetic quantum number of the intermediate atomic state. We also investigate the possibility of nonsequential double detachment with a two-color experiment but observe no evidence for it.