Journal of Physics B Atomic Molecular and Optical Physics

Efficient excitation of Ps by 50-100 fs laser pulses

Lars Bojer Madsen, Lampros A. A. Nikolopoulos, P. Lambropoulos

Published Aug 3, 1999• 10 citations

Abstract

We report on studies of Ps subjected to strong subpicosecond laser pulses. We find substantial deposition of population in excited states extending over a broad range of intensities. The possible usefulness as a source of excited Ps to spectroscopy and the formation of antihydrogen is discussed.

DOI: 10.1088/0953-4075/32/15/103

Related papers

Population of Doubly Excited States in Strong Laser Pulses

Lutz Fechner

Springer thesesJan 1, 20160 citations

Efficient positronium laser excitation for antihydrogen production in a magnetic field

F. Castelli, I. Boscolo, S. Cialdi +2 more

arXiv:0804.0371Physical Review ANov 24, 200858 citations

Observation of dynamic Stark resonances in strong-field excitation

D. Chetty, R. D. Glover, B.A. deHarak +12 more

arXiv:1912.06280Physical Review AMay 4, 202027 citations

Efficient Rydberg positronium laser excitation for antihydrogen production in a magnetic field

(AEGIS Collaboration), M. G. Giammarchi

Springer eBooksJan 1, 20092 citations

Multiphoton resonance in a three-level system with nearly degenerate excited states

Michał Berent, R. Parzyński

arXiv:1007.0371Physical Review AAug 10, 20106 citations

Efficient Rydberg positronium laser excitation for antihydrogen production in a magnetic field

Marco G. Giammarchi

Hyperfine InteractionsSep 1, 20097 citations

Journal of Physics B Atomic Molecular and Optical Physics

Efficient excitation of Ps by 50-100 fs laser pulses

Lars Bojer Madsen, Lampros A. A. Nikolopoulos, P. Lambropoulos

Published Aug 3, 1999• 10 citations

Publisher

Abstract

DOI: 10.1088/0953-4075/32/15/103

Related papers

Population of Doubly Excited States in Strong Laser Pulses

Lutz Fechner

Springer thesesJan 1, 20160 citations

Efficient positronium laser excitation for antihydrogen production in a magnetic field

F. Castelli, I. Boscolo, S. Cialdi +2 more

Antihydrogen production by charge exchange reaction between positronium (Ps) atoms and antiprotons requires an efficient excitation of Ps atoms up to high- $n$ levels (Rydberg levels). In this study it is assumed that a Ps cloud is produced within a relatively strong uniform magnetic field $(1\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ and with a relatively high temperature $(100\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ . Consequently, the structure of energy levels are deeply modified by Zeeman and motional Stark effects. A two-step laser light excitation, the first one from ground to $n=3$ and the second from this level to a Rydberg level, is proposed and the physics of the problem is discussed. We derive a simple formula giving the absorption probability with substantially incoherent laser pulses. A 30% population deposition in high- $n$ states can be reached with feasible lasers suitably tailored in power and spectral bandwidth.Antihydrogen production by charge exchange reaction between positronium (Ps) atoms and antiprotons requires an efficient excitation of Ps atoms up to high-$n$ levels (Rydberg levels). In this study it is assumed that a Ps cloud is produced within a relatively strong uniform magnetic field $(1\phantom{\rule{0.3em}{0ex}}\mathrm{T})$ and with a relatively high temperature $(100\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. Consequently, the structure of energy levels are deeply modified by Zeeman and motional Stark effects. A two-step laser light excitation, the first one from ground to $n=3$ and the second from this level to a Rydberg level, is proposed and the physics of the problem is discussed. We derive a simple formula giving the absorption probability with substantially incoherent laser pulses. A 30% population deposition in high-$n$ states can be reached with feasible lasers suitably tailored in power and spectral bandwidth.

arXiv:0804.0371Physical Review ANov 24, 200858 citations

Observation of dynamic Stark resonances in strong-field excitation

D. Chetty, R. D. Glover, B.A. deHarak +12 more

We investigate AC Stark-shifted resonances in argon with ultrashort near-infrared pulses. Using 30 fs pulses, we observe periodic enhancements of the excitation yield in the intensity regions corresponding to the absorption of 13 and 14 photons. By reducing the pulse duration to 6 fs with only a few optical cycles, we also demonstrate that the enhancements are significantly reduced beyond what is measurable in the experiment. Comparing these to numerical predictions, which are in quantitative agreement with experimental results, we find that even though the quantum state distribution can be broad, the enhancements are largely due to the efficient population of a select few AC Stark-shifted resonant states rather than the closing of an ionization channel. Because these resonances are dependent on the frequency and intensity of the laser field, the broad bandwidth of the 6 fs pulses means that the resonance condition is fulfilled across a large range of intensities. This is further exaggerated by volume-averaging effects, resulting in excitation of the $5g$ state at almost all intensities and reducing the apparent magnitude of the enhancements. For 30 fs pulses, volume averaging also broadens the quantum state distribution, but the enhancements are still large enough to survive. In this case, selectivity of excitation to a single state is reduced below 25% of the relative population. However, an analysis of time-dependent Schr\"odinger equation simulations indicates that excitation of up to 60% into a single state is possible if volume averaging can be eliminated and the intensity can be precisely controlled.We investigate AC Stark-shifted resonances in argon with ultrashort near-infrared pulses. Using 30 fs pulses, we observe periodic enhancements of the excitation yield in the intensity regions corresponding to the absorption of 13 and 14 photons. By reducing the pulse duration to 6 fs with only a few optical cycles, we also demonstrate that the enhancements are significantly reduced beyond what is measurable in the experiment. Comparing these to numerical predictions, which are in quantitative agreement with experimental results, we find that even though the quantum state distribution can be broad, the enhancements are largely due to the efficient population of a select few AC Stark-shifted resonant states rather than the closing of an ionization channel. Because these resonances are dependent on the frequency and intensity of the laser field, the broad bandwidth of the 6 fs pulses means that the resonance condition is fulfilled across a large range of intensities. This is further exaggerated by volume-averaging effects, resulting in excitation of the $5g$ state at almost all intensities and reducing the apparent magnitude of the enhancements. For 30 fs pulses, volume averaging also broadens the quantum state distribution, but the enhancements are still large enough to survive. In this case, selectivity of excitation to a single state is reduced below 25% of the relative population. However, an analysis of time-dependent Schr\"odinger equation simulations indicates that excitation of up to 60% into a single state is possible if volume averaging can be eliminated and the intensity can be precisely controlled.

arXiv:1912.06280Physical Review AMay 4, 202027 citations

Efficient Rydberg positronium laser excitation for antihydrogen production in a magnetic field

(AEGIS Collaboration), M. G. Giammarchi

Springer eBooksJan 1, 20092 citations

Multiphoton resonance in a three-level system with nearly degenerate excited states

Michał Berent, R. Parzyński

An analytic study is presented of the efficient multiphoton excitation and strong harmonic generation in three-level systems specified by a pair of nearly degenerate, strongly dipole-coupled excited states. Such systems are physically formed by the three lowest states in, e.g., the hydrogen atom or evenly charged homonuclear diatomic molecular ions under reasonably chosen laser intensities. As a detailed analytic result, we found that the laser pulse of photon energy $2.05\text{eV}$ , duration $0.23\text{ps}$ , and intensity $5\ifmmode\times\else\texttimes\fi{}{10}^{13}\frac{\mathrm{W}}{{\mathrm{cm}}^{2}}$ is able to produce complete inversion of the initial population in the hydrogen atom through the five-photon excitation. At the same photon energy, the pulse of duration $0.41\text{ps}$ and intensity $3.44\ifmmode\times\else\texttimes\fi{}{10}^{14}\frac{\mathrm{W}}{{\mathrm{cm}}^{2}}$ was found to produce the same effect in the molecular ion but through the nine-photon excitation. We show that the accompanying scattering of light has very rich spectrum differing substantially from that of the two-level system.An analytic study is presented of the efficient multiphoton excitation and strong harmonic generation in three-level systems specified by a pair of nearly degenerate, strongly dipole-coupled excited states. Such systems are physically formed by the three lowest states in, e.g., the hydrogen atom or evenly charged homonuclear diatomic molecular ions under reasonably chosen laser intensities. As a detailed analytic result, we found that the laser pulse of photon energy $2.05\text{eV}$, duration $0.23\text{ps}$, and intensity $5\ifmmode\times\else\texttimes\fi{}{10}^{13}\frac{\mathrm{W}}{{\mathrm{cm}}^{2}}$ is able to produce complete inversion of the initial population in the hydrogen atom through the five-photon excitation. At the same photon energy, the pulse of duration $0.41\text{ps}$ and intensity $3.44\ifmmode\times\else\texttimes\fi{}{10}^{14}\frac{\mathrm{W}}{{\mathrm{cm}}^{2}}$ was found to produce the same effect in the molecular ion but through the nine-photon excitation. We show that the accompanying scattering of light has very rich spectrum differing substantially from that of the two-level system.

arXiv:1007.0371Physical Review AAug 10, 20106 citations

Efficient Rydberg positronium laser excitation for antihydrogen production in a magnetic field

Marco G. Giammarchi

Hyperfine InteractionsSep 1, 20097 citations

Antihydrogen production by charge exchange reaction between positronium (Ps) atoms and antiprotons requires an efficient excitation of Ps atoms up to high-

n

levels (Rydberg levels). In this study it is assumed that a Ps cloud is produced within a relatively strong uniform magnetic field

(1\phantom{\rule{0.3em}{0ex}}\mathrm{T})

and with a relatively high temperature

(100\phantom{\rule{0.3em}{0ex}}\mathrm{K})

. Consequently, the structure of energy levels are deeply modified by Zeeman and motional Stark effects. A two-step laser light excitation, the first one from ground to

n=3

and the second from this level to a Rydberg level, is proposed and the physics of the problem is discussed. We derive a simple formula giving the absorption probability with substantially incoherent laser pulses. A 30% population deposition in high-

n

states can be reached with feasible lasers suitably tailored in power and spectral bandwidth.

5g

state at almost all intensities and reducing the apparent magnitude of the enhancements. For 30 fs pulses, volume averaging also broadens the quantum state distribution, but the enhancements are still large enough to survive. In this case, selectivity of excitation to a single state is reduced below 25% of the relative population. However, an analysis of time-dependent Schr\"odinger equation simulations indicates that excitation of up to 60% into a single state is possible if volume averaging can be eliminated and the intensity can be precisely controlled.

2.05\text{eV}

, duration

0.23\text{ps}

, and intensity $5\ifmmode\times\else\texttimes\fi{}{10}^{13}\frac{\mathrm{W}}{{\mathrm{cm}}^{2}}$ is able to produce complete inversion of the initial population in the hydrogen atom through the five-photon excitation. At the same photon energy, the pulse of duration

0.41\text{ps}

and intensity $3.44\ifmmode\times\else\texttimes\fi{}{10}^{14}\frac{\mathrm{W}}{{\mathrm{cm}}^{2}}$ was found to produce the same effect in the molecular ion but through the nine-photon excitation. We show that the accompanying scattering of light has very rich spectrum differing substantially from that of the two-level system.