We describe the strong field dressing of atomic resonance states, and apply the dressed state description to the photo-excitation of an auto-ionizing resonance, including the effects of radiative and purely transverse line broadenings.
The ordinary Fano effect occurs in many-electron atoms and requires an auto-ionizing state.With such a state, photo-ionization may proceed via pathways that interfere, and the characteristicasymmetric resonance structures appear in the continuum. Here we demonstrate that Fano structure15may also be induced without need of auto-ionization, by dressing the continuum with an ordinarybound state in any atom by a coupling laser. Using multi-photon processes gives complete, ultra-fastcontrol over the interference. We show that a line-shape indexqnear unity (maximum asymmetry)may be produced in hydrogenic silicon donors with a relatively a weak beam. Since the Fanolineshape has both constructive and destructive interference, the laser control opens the possibility20of state-selective detection with enhancement on one side of resonance and invisibility on the other.We discuss a variety of atomic and molecular spectroscopies, and in the case of silicon donors weprovide a calculation for a qubit readout application
The selectivity of three-step pulse photo-ionization of atoms versus the detuning delta of exciting radiation frequencies from intermediate resonance is investigated in powerful laser fields where the power broadening of the resonant transitions is at least of the order of isotope shifts. The Doppler broadening of the resonant transitions is taken into account and it is assumed that the sum frequency of both exciting laser radiations is tuned to the line centre of the two-photon transition of a selected isotope. It is shown that in this situation the photo-ionization selectivity increases so greatly with the absolute detuning mod delta mod that even in such strong fields the process of photo-ionization can be highly selective. The optimization of selective photo-ionization of atoms is discussed in connection with the decrease in the selective isotope yield with increase of the absolute detuning mod delta mod . Analytical consideration of selective three-step pulse photo-ionization in powerful laser fields, based on the density matrix formalism, is presented together with the results of numerical simulation of the 40 Ca- 48 Ca laser isotope separation process as an example.
The ordinary Fano effect occurs in many-electron atoms and requires an autoionizing state. With such a state, photo-ionization may proceed via pathways that interfere, and the characteristic asymmetric resonance structures appear in the continuum. Here we demonstrate that Fano structure may also be induced without need of auto-ionization, by dressing the continuum with an ordinary bound state in any atom by a coupling laser. Using multi-photon processes gives complete, ultra-fast control over the interference. We show that a line-shape index q near unity (maximum asymmetry) may be produced in hydrogenic silicon donors with a relatively weak beam. Since the Fano lineshape has both constructive and destructive interference, the laser control opens the possibility of state-selective detection with enhancement on one side of resonance and invisibility on the other. We discuss a variety of atomic and molecular spectroscopies, and in the case of silicon donors we provide a calculation for a qubit readout application.