Constructive and destructive interferences of Stark resonances induced by an ac field in atomic hydrogen (original) (raw)
Nonponderomotive effects in multiphoton ionization of molecular hydrogen
Physical Review A, 2011
Anomalous photo-electron angular distributions are observed at certain wavelengths in strongfield ionization of H2. We relate this feature to ac-Stark shifts from bound-bound transitions in the Rydberg manifold of principal quantum number n = 3 and 4. A model of the multi-state interaction supports this interpretation.
Stark effect in quasi-hydrogenic species
Le Journal de Physique Colloques
L'analyse des spectres de photoionisation d'atomes à un électron optique en présence d'un champ électrique peut être faite en partant du modèle hydrogénoïde. Le problème de l'effet Stark de l'hydrogène peut être résolu de façon exacte, l'hamiltonien correspondant étant séparable en coordonnées paraboliques. On définit des densités partielles d'états et on montre qu'au-dessus de la limite classique d'ionisation par champ le spectre de l'hydrogène comporte des états quasi-discrets superposés à des états continus, les différents états n'étant pas couplés. Deux expériences concernant les spectres de photoionisation Stark du rubidium montrent l'importance des perturbations liées à l'interaction spin-orbite, comme par exemple la stabilisation d'un état Stark par le champ électrique.
Il Nuovo Cimento D, 1998
We have shown that the amplification without population inversion (AWOPI) from the first excited autoionizing (AI) state of the lL;g symmetry of the H 2 molecules can be obtained when the lowest AI state of the lL;g symmetry is pumped incoherently. We have considered a resonant two-photon transition scheme from the ground X1L;g(v O,j 1) state to the ionization continuum embracing the two AI states (the lowest and the first excited autoionizing states) of the 1 L;g symmetry via the resonant intermediate B 1 L;u (v 4, j 2) level. The effect of two-photon nearresonant autoionizing channels via the near-resonant rovibrationallevels of the B 1 L;u state has also been considered. We have found that the gain can be obtained in different spectral regions corresponding to the resonances with the lowest and first excited AI states from the intermediate levels of the B 1 L;u state. The inherent coherence between two AI states due to the configuration interaction coupling via the common continuum has been found to have a significant effect on the amplification process, which occurs around all the resonance frequencies connecting this AI state with the intermediate levels. This gain can be significantly modified by increasing the coupling strength of this excited AI state with the continuum. Moreover, the gain from the excited AI state remains unaffected by the damping caused by incoherent pumping to the lowest AI state. It has also been shown that the persistence of inversionless gain from the excited AI state is shorter than that from the lowest AI state. The presence of close-lying near-resonant rovibrationallevels leads to the increase in gain around the resonances with two AI states from the B1L;u (v 4,j 2) level. The advantages of this type of scheme are; i) AWOPI can be obtained from an excited AI state although it has not been pumped and Ii) the amplification obtained from the excited AI state is almost unaffected by the distortion caused by incoherent pumping to the lower AI state. PACS 42.55.Ah-General laser theory. PACS 42.50.Hz-Strong-field excitation of optical transitions in quantum systems; multiphoton processes; dynamic Stark shift.
Controlled strong non-dipole effects in photoionization of confined atoms
Journal of Physics B: Atomic, Molecular and Optical Physics, 2000
It is demonstrated that non-dipole effects in low energy photoionization of atoms surrounded by a repulsive semi-transparent potential can be increased by many orders of magnitude due to virtual levels occuring in the spectra of photoelectrons as a result of confinement. The strengths, widths and positions of such resonances in non-dipole channels can be controlled by altering the characteristics of the confining potential, and under certain circumstances can be so large that treating quadrupole transitions as a perturbation breaks down, even for photon energies as low as tens of eV. Our conclusions have relevance to the interpretation of non-dipole photoemission spectra from solids, molecules, atoms trapped inside fullerene molecules, quantum dots, etc. Non-dipole electric-dipole-electric-quadrupole (E1-E2) interference effects in angular distribution spectra of photoelectrons due to photoionization of free atoms have attracted much attention in recent years, both from theorists (
Rydberg hydrogen atom near a metallic surface: Stark regime and ionization dynamics
Physical Review A, 2007
We investigate the classical dynamics of a hydrogen atom near a metallic surface in the presence of a uniform electric field. To describe the atom-surface interaction we use a simple electrostatic image model. Owing to the axial symmetry of the system, the z-component of the canonical angular momentum P is an integral and the electronic dynamics is modeled by a two degrees of freedom Hamiltonian in cylindrical coordinates. The structure and evolution of the phase space as a function of the electric field strength is explored extensively by means of numerical techniques of continuation of families of periodic orbits and Poincaré surfaces of section. We find that, due to the presence of the electric field, the atom is strongly polarized through two consecutive pitchfork bifurcations that strongly change the phase space structure. Finally, by means of the phase space transition state theory and the classical spectral theorem, the ionization dynamics of the atom is studied.
Different approach to the Stark effect: Application to the hydrogen ground state
Physical Review A, 1990
A method is proposed to evaluate the energy levels and wave functions of atomic hydrogen in a uniform electric field. A self-consistent criterion is used and the method proves to be sufficiently accurate and easy to implement even for high electric-field strengths. We present the results obtained for the ground-state level and compare them with those obtained by other authors. 'Perturbation theory (see Ref. 3). Reference 4. 'Reference S. Values for polynomials of degree 15.
Electric-Field Induced Dipole Blockade with Rydberg Atoms
Physical Review Letters, 2007
High resolution laser Stark excitation of np (60 < n < 85) Rydberg states of ultra-cold cesium atoms shows an efficient blockade of the excitation attributed to long-range dipole-dipole interaction. The dipole blockade effect is observed as a quenching of the Rydberg excitation depending on the value of the dipole moment induced by the external electric field. Effects of eventual ions which could match the dipole blockade effect are discussed in detail but are ruled out for our experimental conditions. Analytic and Monte-Carlo simulations of the excitation of an ensemble of interacting Rydberg atoms agree with the experiments indicates a major role of the nearest neighboring Rydberg atom.