A dressed-atom approach to resonance fluorescence in intense laser fields is presented. Simple and general results are derived which include the now well known predictions concerning two-level atoms but are not restricted to such simple cases. The positions of the various components of the fluorescence and absorption spectra are given by the allowed Bohr frequencies of the total system: atom+laser mode (dressed atom). The master equation, describing spontaneous emission from the dressed atom is solved in the limit of high intensities. Simple expressions, taking into account the effect of cascades, are derived for the widths of the components.
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L A Vainshtein and A V Vinogradov 1970 J. Phys. B: Atom. Mol. Phys. 3 1762
G C King et al 1977 J. Phys. B: Atom. Mol. Phys. 10 3357
C Cohen-Tannoudji and S Reynaud 1977 J. Phys. B: Atom. Mol. Phys. 10 345
H J Carmichael 1980 J. Phys. B: Atom. Mol. Phys. 13 3551
The cooperative resonance fluorescence steady state is discussed within the context of an operator master equation which conserves total pseudospin. Emphasis throughout is on quantum fluctuations and their significance in relation to a background of factorised dynamics. Atom-atom correlations are shown to play a fundamental role for systems driven beyond the linear regime. Use of the atomic coherent state representation yields a Fokker-Planck description closely allied to the dynamics for a classical angular momentum oscillator. For intense incident fields the quantum-mechanical steady state is understood in terms of diffusion both around and between classical trajectories on the Bloch sphere. In the limit of infinite systems simple closed-form expressions for steady-state features are derived. Coherent and incoherent fluorescent intensities are obtained together with the second-order correlation function for fluorescent light. Specific features are illustrated by numerical results for systems of from two to fifty atoms.
H J Carmichael and D F Walls 1976 J. Phys. B: Atom. Mol. Phys. 9 1199
The description begins with an operator master equation for the atom plus incident field. Reduced atomic matrix elements are derived for arbitrary field strengths. First- and second-order correlation functions in the scattered field are also obtained and discussed in relation to the scattered spectrum and intensity-fluctuation measurements. This formalism has the appealing feature that all information is readily available from the one set of four coupled equations. The deficiencies in both the one-photon approximation and the semiclassical perspective are established in a natural and transparent fashion.
W P Healy and R G Woolley 1978 J. Phys. B: Atom. Mol. Phys. 11 1131
It is shown that the on-energy-shell single-particle scattering amplitudes obtained from the minimal-coupling and the multipolar forms of the Hamiltonian in non-relativistic quantum electrodynamics are equal to order e2; both forms of the Hamiltonian thus lead to the same differential cross section for Kramers-Heisenberg scattering. The proof given is based directly on the relations which hold between the two transition matrices and is simpler than a previous proof which relied on sum rules derived from the canonical commutation relations. The proof is also more general in that the multipolar Hamiltonian is defined in terms of line integrals along paths which are not assumed to be straight lines but which can be chosen from a large class of possible curves.
N S Scott et al 1982 J. Phys. B: Atom. Mol. Phys. 15 4647
M Lindberg and S Stenholm 1984 J. Phys. B: Atom. Mol. Phys. 17 3375
The authors consider the laser cooling of a trapped two-level system during its final approach to equilibrium. Then it moves only within one optical wavelength and an expansion in the Lamb-Dicke parameter is possible. This allows an adiabatic elimination of the internal degrees of freedom. There remains a slow time evolution on a new time scale related to the Lamb-Dicke parameter. This scale is determined by an effective time evolution operator, which the authors derive using the method of degenerate perturbation theory. The ensuing master equation can be completely solved both for its time evolution and the ultimate steady state. In addition to providing a complete description of the final stages of the laser cooling, the calculation can be seen to add one more soluble case to the discussion of non-equilibrium statistical mechanics.
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U Wille 1987 J. Phys. B: Atom. Mol. Phys. 20 6669
M Kimura et al 1987 J. Phys. B: Atom. Mol. Phys. 20 6670
N N Choi et al 1987 J. Phys. B: Atom. Mol. Phys. 20 L827
Non-relativistic rates for the decay of 2s hydrogen atoms to the ground state by single-photon and two-photon emission in the presence of a homogeneous magnetic field of arbitrary strength (0<or=B<or=4.7*106 T) are calculated by variational procedures. Over the whole range of B, two-photon emission is the dominant process. As the magnetic field grows, the two-photon decay rate increases. It is found that the Markov approximation can be applied to the two-photon decay for magnetic fields of strength B>or=4.7*103 T.
B Wallbank et al 1987 J. Phys. B: Atom. Mol. Phys. 20 L833
Differential cross sections for the one-photon emission free-free process are measured as a function of laser intensity when 10.55 eV electrons are scattered from argon atoms in the presence of a pulsed CO2 laser. The cross sections are reported for both single longitudinal-mode and multimode laser pulses up to an intensity of 2*107 W cm-2. For intensities less than 2*106 W cm-2, the cross sections for both laser pulses are found to be linear with intensity, in agreement with perturbation theory. At higher intensities comparisons are made with predictions based on the low-frequency approximation and two laser models. The linear parts of the cross sections are used to obtain estimates of the spatial inhomogeneities in the electron-laser interaction region. Reasonable agreement is found between the experimental cross sections and those predicted by the two laser models.
Y Vitel and M Skowronek 1987 J. Phys. B: Atom. Mol. Phys. 20 6477
Stark widths and shifts of the Ar I 696.5 nm and of the Ar II 480.6, 484.7 and 434.8 nm lines have been measured in the range of electron density and temperature 0.6-1.5*1018 cm-3, 16200-18700 K. These high-density plasmas are created in linear flash-tubes. The plasma parameters are principally determined by measurements of the continuum radiation, from the intensity of optically thick lines in their centre and by the condition of local thermodynamic equilibrium of the plasma. The electron density and temperature radial profiles so deduced are found to be practically flat over more than half of the tube radius. In this quasi-stationary stage of the plasma, the experimental line profiles are recorded by an optical multichannel analyser coupled with a high-dispersion spectrometer. The profiles are analysed and fitted to a Lorentzian function. The Stark parameters, width and shift, show a non-linear dependence against the electron density.
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B E J Pagel 1971 J. Phys. B: Atom. Mol. Phys. 4 279
The following applications of spectral line broadening theory to astrophysics are briefly reviewed: (i) understanding qualitative effects visible on spectrograms; (ii) quantitative understanding of hydrogen-line profiles for the determination of stellar atmospheric parameters; (iii) effects of line broadening on the determination of stellar chemical composition.