A dynamic equation of atoms irradiated by a laser light in a magnetic field is applied to the light modulation experiment of atoms, whose excited states are not optically connected with the ground state. The resonance for the fluorescent light as a function of magnetic field is derived. The resonance curve for the fluorescent light from the lower level is found to be a superposition of resonance curves of two different widths. The broad component is a manifestation of the atomic coherence of the lower level. The narrow component is attributed to the atomic coherence of the upper level which is transferred to the lower level by spontaneous emission. The decay rate of the upper level is included in the expression of the resonance curve for the fluorescent light from the lower level.
A dynamic equation of atoms irradiated by a laser light in a magnetic field is applied to the light modulation experiment of atoms, whose excited states are not optically connected with the ground state. The resonance for the fluorescent light as a function of magnetic field is derived. The resonance curve for the fluorescent light from the lower level is found to be a superposition of resonance curves of two different widths. The broad component is a manifestation of the atomic coherence of the lower level. The narrow component is attributed to the atomic coherence of the upper level which is transferred to the lower level by spontaneous emission. The decay rate of the upper level is included in the expression of the resonance curve for the fluorescent light from the lower level.
In this experiment Xe atoms are pumped to the excited states with an r.f. discharge and irradiated by the 3.99 µm Xe laser on the 5d[1/2] 0 0 →6p[1/2] 1 transition. Fluorescent light from the 6p[1/2] 1 level is observed to be modulated when the atoms are subjected to a low-frequency rotating field in perpendicular to the static field. The natural lifetime of the 6p[1/2] 1 level is obtained to be 56±3 ns. The 3.50 µm laser on the 5d[7/2] 0 3 →6p[5/2] 2 transition is also used. The light modulation signal of the fluorescence from the 6p[5/2] 2 level as a fuction of the magnetic field is a superposition of resonance curves of two different widths. The narrow component is a manifestation of atomic coherence of the 5d[7/2] 0 3 level which is transferred to the 6p[5/2] 2 level. The natural lifetime of the 5d[7/2] 0 3 level is obtained as 73±9 ns from the study of the 6p[5/2] 2 level.
Abstract A theory is formulated to describe the modulation which has been observed in fluorescent light from atoms subjected simultaneously to optical and radio-frequency radiation. The optical field stimulates one or more of a set of excited states of the atom, between which the radio-frequency field establishes coherence. This coherence is manifest in the fluorescent radiation. Interference between radiations of different frequency leads to modulation. General expressions are given for the intensity of the fluorescent light as a function of time. The Zeeman structure of the transition (63P1 — 6 1S0), A2537 A, in mercury is studied in detail. Modulation at frequencies, 1, 2, 3 and 4 times that of the radio-frequency field, w0, is predicted, and resonant effects at static magnetic fields, 0, 1/2, 1, 3/2, 2 and 3 times H0, the field for which w0 is the Larm or frequency. Resonances at fields other than H0 are due to excitation with light of mixed polarization. Most of the predicted effects have been found experimentally. A ‘frequency diagram’ is introduced and discussed, to represent the combined effects of static and radio-frequency magnetic fields. To each excited state belong a set of r frequencies, where r is the number of states linked by the radio-frequency perturbation. The 9 levels are drawn, as functions of H, for the states mJ = 0, ± 1, of 3P1. The resonances at fields other than H0 may be associated with intersections of frequency levels belonging to different mJ.
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.
A treatment of resonance fluorescence is given in which the properties of the incident and scattered light are expressed in terms of coherency matrices. Calculations are made for two successive scattering processes corresponding to the experiments described in an accompanying paper. For the first process the scattering atoms are subjected to a magnetic field consisting of parallel static and oscillating components. The fluorescent light is frequency-modulated and may also be polarization-modulated. This light excites fluorescence in a second cell in which the atoms are subjected to a static magnetic field. The equations show under what conditions the second fluorescence is intensity-modulated and describe the resonances in the amplitude of modulation which occur when the modulation frequency matches a Zeeman interval of the excited atoms.
Abstract This is an investigation, at low frequencies, of the modulation of fluorescent light which has already been found a t higher frequencies in a double resonance experiment. In the earlier work, in which the frequency of magnetic resonance was of order 10 Mc/s, the Zeeman levels of the excited atom s were well separated compared with their natural width (1 M c/s): in the present work they are completely unresolved at the centre of the magnetic resonance, which is studied a t 1 kc/s. The principal resonance phenomena are observed as before under the new conditions: they are centred on a field near to zero, while their width is greater than 1G. New resonance phenomena are also studied, which do not appear when the resonance frequency is greater than the natural width of the levels. A theory, previously published, is applied to predict the form of the new resonance curves. An identical result is predicted by the use of a classical model.
For pt.I see ibid., vol.12, no.12, p.1939 (1979). The modulated fluorescence in an optical double resonance experiment, i.e. when an atom interacts with two intense monochromatic laser beams each of which is weakly modulated in amplitude at frequency Omega , is studied in detail. The modulation rate corresponding to the steady-state population of the highest atomic level exhibits resonant structures at the modulation frequencies Omega =0, +or- alpha 0 , +or-2 alpha 0 due to the dynamical Stark splitting of the various energy levels; alpha 0 being related to the Rabi frequencies alpha 1 and alpha 2 associated with the two lasers and the two atomic transitions, by alpha 0 2 = mod alpha 1 mod 2 + mod alpha 2 mod 2 . The peak at Omega =+or- alpha 0 is the most intense and exhibits splitting when the applied fields are detuned from exact resonance with the respective atomic frequencies. Resonances are observed in the modulation rate of the intermediate-level population at the modulation frequencies Omega =0, +or-2 alpha 0 . In the presence of detunings of the applied fields, additional resonant structures occur at Omega =+or- alpha 0 which increase in magnitude with higher detunings and split. Explicit expressions for the positions, widths and weights of these resonant components are obtained analytically for intense, resonant fields. Numerical results for general values of the laser field strengths and the detunings are given.