Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physica Scripta

Effect of Radiative Relaxation of Excitation Anisotropy on the Measurement of Atomic Lifetime. Demonstration on Argon 2p4Level

Takashi Fujimoto, Chiaki Goto, Yasunori Uetani, Kuniya Fukuda

Published Dec 1, 1983• 15 citations
Publisher

Abstract

We have measured the atomic lifetime of the argon 2 p 4 level by the laser-induced-fluorescence spectroscopy to be 30.5 ns. This contradicts the recent measurement using the high-frequency plused electron-beam excitation. We conjecture that, in their experiment, the radiation trapping not only affects the decay of the upper-level population but also relaxes the alignment initially produced by the electron-collision excitation in the upper-level population. Thus, the directly observed decay of the emission-line intensity is different from the decay of the upper-level population. We have observed the radiative relaxation of alignment on the neon 2 p 2 level which is a complementary effect to coherence narrowing.

DOI
10.1088/0031-8949/28/6/005

Related papers

Polarization effects and depolarizing collisions in atomic vapour and molecular gas

Хворостов Евгений Борисович, Н. Н. Рубцова, В. Н. Ищенко +3 more

Polarization effects in gases are investigated by two methods of coherent spectroscopy - stimulated photon echo in molecular gas and laser-induced fluorescence in atomic vapour. A well developed photon echo experimental technique permitted us not only to measure relaxation rates of population, orientation and alignment on degenerated resonant levels in molecular gas but also to study their dependence on particles' longitudinal velocity. The degree of polarization of laser-induced fluorescence in Yb vapour in a mixture with Xe proves a large contribution of depolarizing collisions. The complicated non-exponential fluorescence decay at higher Yb pressures is explained by the radiation trapping.

Journal of Optics B Quantum and Semiclassical Optics•Apr 1, 2001•0 citations

Effects of radiative decay in four-wave-mixing spectroscopy: Narrow resonances produced by nonconservation of population, alignment, and orientation

P. R. Berman, Duncan G. Steel, G. Khitrova +1 more

We present experimental and theoretical results describing the presence of radiative-decay-induced narrow resonances in systems which do not conserve population, alignment, or orientation. We show how spectroscopic line-shape analysis of the nonlinear response can be used to determine all of the relaxation parameters characterizing a two-level atom.

Physical Review A•Jul 1, 1988•61 citations

Disalignment of excited atoms by radiation re-absorption: neon 2p2atoms in a discharge plasma

Manabu Seo, Masanori Nimura, Masahiro Hasuo +1 more

In a positive column of a glow discharge, a linearly polarized laser pulse produces aligned neon atoms in the 2p 2 (Paschen notation) level, and the subsequent fluorescence is observed with its polarized components resolved. The relaxation rate of the alignment, or the disalignment rate, is thus determined. The populations of the 1s 2 – 1s 5 levels are found to be strongly dependent on the discharge current, and so are the degrees of radiation re-absorption of the transition lines from 2p 2 to these levels. A Monte Carlo simulation is performed by which the disalignment rate by radiation re-absorption for these transitions is determined, where the isotope splitting of the transition lines is taken into account. This rate is subtracted from the observed disalignment rate, resulting in the rate being independent of the degree of radiation re-absorption. Thus, disalignment due to atom collisions and that due to radiation re-absorption are separated. For the latter disalignment the disalignment rate deduced by the simulation, treating the four transitions simultaneously, is found to be virtually equal to the sum of the disalignment rates for each of the transitions. The approximate expression for the disalignment rate given by D’Yakonov and Perel’ (1965 Sov. Phys.–JETP 20 997) is quantified, so that it can be applied to estimating the disalignment rate of an upper level having several transition lines with finite optical thickness.

Journal of Physics B Atomic Molecular and Optical Physics•Apr 24, 2003•15 citations

Polarization of the fluorescent light of Ne atoms interacting with a laser beam measurement of several relaxation times

Bernard Decomps, M. Dumont

The fluorescent light from two atomic levels is studied assuming that the atoms are subjected to a gas discharge, to a static magnetic field, and, simultaneously, to a laser beam having the transition frequency between the atomic levels. Calculations are developed in the formalism of irreducible tensor operators. One takes into account the existence of isotropic relaxations and cascade effects due to spontaneous emission between the upper and the lower levels. Following Lamb, the laser beam is described classically by its electric field, and its effects are calculated by perturbation theory. It is predicted that the σ component of fluorescent light exhibits the Hanle effect, which allows one to measure the relaxation rates\Gamma(0)and\Gamma(2)of the population and of the alignment of the emitting level, respectively. Experimental agreement with the theoretical analysis has been found for the3s_{2}, 2s_{2}, and2P_{4}levels of Ne. Among the experimental results obtained by this method are the natural widths and the collision cross sections for population (quenching collision) and for alignment. Several transition probabilities are also derived. Furthermore, the theory of coherent imprisonment of the fluorescent line has been found valid even if laser pumping light is used.

IEEE Journal of Quantum Electronics•Nov 1, 1968•45 citations

Two-photon Resonant Excitation Of Thallium In An Atomic Beam (multiphoton, Radiative Lifetimes).

John V. James

We have observed fluorescence and ionization signals resulting from two-photon resonant excitation of thallium in an atomic beam. The output of a pulsed dye laser is used to excite the resonance between the ground state (6('2)P(,1/2)) and an excited n('2)P state of thallium. Both two-photon absorption and three-photon absorption occur simultaneously; the latter results in photoionization of the atom. The excited states populated by two-photon absorption decay via cascade fluorescence back to the ground state; one or more of these spectral components constitute our fluorescence signal. The lifetimes of the excited n('2)P states of thallium have been measured directly by observing the exponential decay of this fluorescence. Calculations are included to ascertain the time required for the fluorescence signal to reach within 2% of a simple exponential decay. This decay is a measure of the lifetime of the initial state, under the condition that none of the fluorescence components arise from states which are populated by cascade through longer-lived states. The lifetimes of the n('2)P(,1/2) and n('2)P(,3/2) states of thallium for n = 7 to 11 are determined in this manner and compared with the values deduced from semi-empirical calculations of oscillator strengths by various authors. For calculations employing the effects of core polarizability in the electron wavefunctions and in the transition matrix elements, the agreement is very good--to within our experimental uncertainty, which is typically(, )<5%. Our measurements are also compared to the four other known experimental values for such excited states of thallium. Some of these previous experiments and calculations were carried out in conjunction with parity non-conservation experiments in thallium. Our measurements may provide useful checks on the accuracy of some of the calculations performed in the evaluation of such experiments. The ionization and fluorescence signals are also studied under conditions of strong saturation of the two-photon resonance with the 7('2)P states. The manifestation of saturation in the ionization signal is a broadening of the excitation spectrum, which is found to greatly exceed that of the fluorescence signal. Furthermore, the ratio of the ionization signal to the fluorescence signal at the peak of the resonance is found to vary linearly at intensities below about 10('9) W/cm('2); this too saturates at higher intensities. Various models are employed to simulate the observed behavior, encompassing both rate equations as well as density matrix formulations. The numerical solutions to these models are compared with the observed behavior; the agreement is found to depend strongly on the assumed experi- mental conditions to which the ensemble of atoms is subjected.

•Jan 1, 1986•0 citations

Effect of collisions on the resonance fluorescence spectrum

А. И. Пархоменко, Anatolii M. Shalagin

The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.

Journal of Experimental and Theoretical Physics•May 1, 2008•1 citation
We have measured the atomic lifetime of the argon 2 p 4 level by the laser-induced-fluorescence spectroscopy to be 30.5 ns. This contradicts the recent measurement using the high-frequency plused electron-beam excitation. We conjecture that, in their experiment, the radiation trapping not only affects the decay of the upper-level population but also relaxes the alignment initially produced by the electron-collision excitation in the upper-level population. Thus, the directly observed decay of the emission-line intensity is different from the decay of the upper-level population. We have observed the radiative relaxation of alignment on the neon 2 p 2 level which is a complementary effect to coherence narrowing.
Polarization effects in gases are investigated by two methods of coherent spectroscopy - stimulated photon echo in molecular gas and laser-induced fluorescence in atomic vapour. A well developed photon echo experimental technique permitted us not only to measure relaxation rates of population, orientation and alignment on degenerated resonant levels in molecular gas but also to study their dependence on particles' longitudinal velocity. The degree of polarization of laser-induced fluorescence in Yb vapour in a mixture with Xe proves a large contribution of depolarizing collisions. The complicated non-exponential fluorescence decay at higher Yb pressures is explained by the radiation trapping.
In a positive column of a glow discharge, a linearly polarized laser pulse produces aligned neon atoms in the 2p 2 (Paschen notation) level, and the subsequent fluorescence is observed with its polarized components resolved. The relaxation rate of the alignment, or the disalignment rate, is thus determined. The populations of the 1s 2 – 1s 5 levels are found to be strongly dependent on the discharge current, and so are the degrees of radiation re-absorption of the transition lines from 2p 2 to these levels. A Monte Carlo simulation is performed by which the disalignment rate by radiation re-absorption for these transitions is determined, where the isotope splitting of the transition lines is taken into account. This rate is subtracted from the observed disalignment rate, resulting in the rate being independent of the degree of radiation re-absorption. Thus, disalignment due to atom collisions and that due to radiation re-absorption are separated. For the latter disalignment the disalignment rate deduced by the simulation, treating the four transitions simultaneously, is found to be virtually equal to the sum of the disalignment rates for each of the transitions. The approximate expression for the disalignment rate given by D’Yakonov and Perel’ (1965 Sov. Phys.–JETP 20 997) is quantified, so that it can be applied to estimating the disalignment rate of an upper level having several transition lines with finite optical thickness.
The fluorescent light from two atomic levels is studied assuming that the atoms are subjected to a gas discharge, to a static magnetic field, and, simultaneously, to a laser beam having the transition frequency between the atomic levels. Calculations are developed in the formalism of irreducible tensor operators. One takes into account the existence of isotropic relaxations and cascade effects due to spontaneous emission between the upper and the lower levels. Following Lamb, the laser beam is described classically by its electric field, and its effects are calculated by perturbation theory. It is predicted that the σ component of fluorescent light exhibits the Hanle effect, which allows one to measure the relaxation rates\Gamma(0)and\Gamma(2)of the population and of the alignment of the emitting level, respectively. Experimental agreement with the theoretical analysis has been found for the3s_{2}, 2s_{2}, and2P_{4}levels of Ne. Among the experimental results obtained by this method are the natural widths and the collision cross sections for population (quenching collision) and for alignment. Several transition probabilities are also derived. Furthermore, the theory of coherent imprisonment of the fluorescent line has been found valid even if laser pumping light is used.
We have observed fluorescence and ionization signals resulting from two-photon resonant excitation of thallium in an atomic beam. The output of a pulsed dye laser is used to excite the resonance between the ground state (6('2)P(,1/2)) and an excited n('2)P state of thallium. Both two-photon absorption and three-photon absorption occur simultaneously; the latter results in photoionization of the atom. The excited states populated by two-photon absorption decay via cascade fluorescence back to the ground state; one or more of these spectral components constitute our fluorescence signal. The lifetimes of the excited n('2)P states of thallium have been measured directly by observing the exponential decay of this fluorescence. Calculations are included to ascertain the time required for the fluorescence signal to reach within 2% of a simple exponential decay. This decay is a measure of the lifetime of the initial state, under the condition that none of the fluorescence components arise from states which are populated by cascade through longer-lived states. The lifetimes of the n('2)P(,1/2) and n('2)P(,3/2) states of thallium for n = 7 to 11 are determined in this manner and compared with the values deduced from semi-empirical calculations of oscillator strengths by various authors. For calculations employing the effects of core polarizability in the electron wavefunctions and in the transition matrix elements, the agreement is very good--to within our experimental uncertainty, which is typically(, )<5%. Our measurements are also compared to the four other known experimental values for such excited states of thallium. Some of these previous experiments and calculations were carried out in conjunction with parity non-conservation experiments in thallium. Our measurements may provide useful checks on the accuracy of some of the calculations performed in the evaluation of such experiments. The ionization and fluorescence signals are also studied under conditions of strong saturation of the two-photon resonance with the 7('2)P states. The manifestation of saturation in the ionization signal is a broadening of the excitation spectrum, which is found to greatly exceed that of the fluorescence signal. Furthermore, the ratio of the ionization signal to the fluorescence signal at the peak of the resonance is found to vary linearly at intensities below about 10('9) W/cm('2); this too saturates at higher intensities. Various models are employed to simulate the observed behavior, encompassing both rate equations as well as density matrix formulations. The numerical solutions to these models are compared with the observed behavior; the agreement is found to depend strongly on the assumed experi- mental conditions to which the ensemble of atoms is subjected.
The effect of collisions on the resonance fluorescence spectrum of two-level atoms excited by monochromatic resonance radiation is studied. Analysis is performed for systems where the Doppler broadening is small compared to the collision frequency (high buffer gas pressures) and for the general case where collisions arbitrarily change the phase of the radiation-induced dipole moment (from completely interrupted to completely unaffected phase of the dipole moment). Both at a relatively low and at a high excitation radiation intensity, the resonance fluorescence spectrum is shown to depend on whether the two-level system is closed or open. This is especially true for the narrow unshifted Rayleigh scattering line. It is shown that, although the absorption line is homogeneously broadened, the resonance fluorescence spectrum exhibits a clearly pronounced anisotropy. In a direction close to the direction of propagation of the excitation radiation, the Rayleigh scattering line is maximally narrowed. Under certain conditions (that can easily be created in experiments), the width of this line is proportional to the diffusion coefficient of atoms interacting with the radiation.