dorsal/arxiv
View SchemaNon-relativistic quantum electrodynamics for strong laser-atom interaction
| Authors | Marco Frasca |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0004002 |
| URL | https://arxiv.org/abs/quant-ph/0004002 |
Abstract
A formulation of quantum electrodynamics is given that applies to atoms in a strong laser field by perturbation theory in a non-relativistic regime. Dipole approximation is assumed. The dual Dyson series, here discussed by referring it to the Birkhoff theorem for singularly perturbed linear differential equations, can be applied and a perturbation series obtained transforming the Hamiltonian by a Pauli-Fierz transformation. But, if just few photons are present high-order harmonics cannot be generated. So, it is proven that odd high-order harmonics only appear when the laser field is intense and one can substitute the creation and annihilation operators by the square root of the mean number of photons taken to be huge, the field retaining its coherency property as observed experimentally for harmonics. In this case, the Hamiltonian for perturbation theory comes to the Kramers-Henneberger form. The theory has a dipolar contribution when the free-electron quiver motion amplitude is larger than the atomic radius. For a Coulomb potential one has that the outer electron is periodically kicked, and so a prove is given that the same should happen to Rydberg atoms in intense microwave fields. The distribution representing the kicking has a Fourier series with just odd terms. Using a modified Rayleigh-Schr\"odinger perturbation theory, it is shown that under the same condition of validity of the quiver motion amplitude to atomic radius ratio, the atomic wave function is only slightly modified by the laser field due to the way the energy levels rearrange themselves. This gives a prove of stabilization in the limit of laser frequency going to infinity. Then, perturbation theory can be applied when the Keldysh parameter becomes smaller with respect to the shifted distance between the energy levels of the atom.
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"abstract": "A formulation of quantum electrodynamics is given that applies to atoms in a\nstrong laser field by perturbation theory in a non-relativistic regime. Dipole\napproximation is assumed. The dual Dyson series, here discussed by referring it\nto the Birkhoff theorem for singularly perturbed linear differential equations,\ncan be applied and a perturbation series obtained transforming the Hamiltonian\nby a Pauli-Fierz transformation. But, if just few photons are present\nhigh-order harmonics cannot be generated. So, it is proven that odd high-order\nharmonics only appear when the laser field is intense and one can substitute\nthe creation and annihilation operators by the square root of the mean number\nof photons taken to be huge, the field retaining its coherency property as\nobserved experimentally for harmonics. In this case, the Hamiltonian for\nperturbation theory comes to the Kramers-Henneberger form. The theory has a\ndipolar contribution when the free-electron quiver motion amplitude is larger\nthan the atomic radius. For a Coulomb potential one has that the outer electron\nis periodically kicked, and so a prove is given that the same should happen to\nRydberg atoms in intense microwave fields. The distribution representing the\nkicking has a Fourier series with just odd terms. Using a modified\nRayleigh-Schr\\\"odinger perturbation theory, it is shown that under the same\ncondition of validity of the quiver motion amplitude to atomic radius ratio,\nthe atomic wave function is only slightly modified by the laser field due to\nthe way the energy levels rearrange themselves. This gives a prove of\nstabilization in the limit of laser frequency going to infinity. Then,\nperturbation theory can be applied when the Keldysh parameter becomes smaller\nwith respect to the shifted distance between the energy levels of the atom.",
"arxiv_id": "quant-ph/0004002",
"authors": [
"Marco Frasca"
],
"categories": [
"quant-ph",
"hep-ph",
"hep-th",
"physics.atom-ph"
],
"title": "Non-relativistic quantum electrodynamics for strong laser-atom interaction",
"url": "https://arxiv.org/abs/quant-ph/0004002"
},
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