Obtaining an accurate value of the electric dipole moment μ is essential in the fields of laser application technologies. A direct way of measuring the electric dipole moment μ is to observe the Rabi-oscillation which manifests itself in the coherent photo-excitation behavior of atoms. In the case of the elements which have large angular momenta, identifying the Rabi-oscillation in their excitation behavior becomes rather difficult. We proposed an accurate and straightforward method of determining the electric-dipole moment μ between multifold degenerate levels. The point is to remove the degeneracy by applying an external magnetic field with the aid of the Zeeman effect and, then, to realize a degeneration free coherent excitation. As a result, we can observe the Rabi-oscillations explicitly in the excitation vs. laser-fluence curves. The present method provides a reliable basis of experimental determination of μ. As an example, we applied the present method to a transition to 0–17,362 cm−1 level in uranium and obtained the value μ=0.86±0.06 (Debye).
Obtaining an accurate value of the electric dipole moment μ is essential in the fields of laser application technologies. A direct way of measuring the electric dipole moment μ is to observe the Rabi-oscillation which manifests itself in the coherent photo-excitation behavior of atoms. In the case of the elements which have large angular momenta, identifying the Rabi-oscillation in their excitation behavior becomes rather difficult. We proposed an accurate and straightforward method of determining the electric-dipole moment μ between multifold degenerate levels. The point is to remove the degeneracy by applying an external magnetic field with the aid of the Zeeman effect and, then, to realize a degeneration free coherent excitation. As a result, we can observe the Rabi-oscillations explicitly in the excitation vs. laser-fluence curves. The present method provides a reliable basis of experimental determination of μ. As an example, we applied the present method to a transition to 0–17,362 cm−1 level in uranium and obtained the value μ=0.86±0.06 (Debye).
Most conventional methods of determining the dipole moment μ are unsatisfactory when applied to transitions between degenerate levels; this is because the overlapping of transitions among magnetic sub‐levels modifies the photo‐excitation behavior in a complex way. To overcome this difficulty, two novel methods of determination are presented. One makes use of differently polarized laser light, and yields a set of excitation curves specific to each polarization. By treating μ as a parameter and fitting the curves through calculations, one can obtain the value of μ. In the other method, a magnetic field is applied to the atom under study in order to raise its degeneracy. As a result, simple Rabi oscillations manifest themselves and one can derive μ directly from their frequencies. These two methods of determining μ are tested on absorption lines in uranium, demonstrating that they work quite well and improve the accuracy of measured dipole moments.
A simple and straightforward method is presented for determining the electric-dipole moments of phototransitions between degenerate levels in atoms. In the present method, the dynamic Stark effect (DSE) is induced by a high-fluence laser light in the presence of a strong external magnetic field. The energy splitting caused by the DSE is measured by sweeping the frequency of the probe laser. As the separation width of the DSE peak is essentially given by a product of the dipole moment , the relevant Wigner 3- j symbol and the square root of the laser intensity, we are able to determine the value of in a direct way. As the DSE is induced between a pair of non-degenerate Zeeman sublevels, which is singled out by the external magnetic field, the result is free from any ambiguities brought about by the degeneracy such as the smoothing out of DSE peaks caused by the overlapping of the sublevel contributions. The method was tested against the transition between the 17 362 and levels in atomic uranium, giving the electric dipole moment .
We report here the first observation and measurement of the transition magnetic moment for a strongly forbidden S-S transition of an alkali atom. By using single-photon excitation of the 6S1/2-7S1/2 caesium transition in a quasi-static electric field, we have detected an electronic polarization of the excited state, specific to an interference effect occurring in mixed electric magnetic dipole transitions. Our measurements, independent of the vapour density, indicate that the magnetic dipole amplitude M 1 has the same size as the electric dipole amplitude E1 , induced by an electric field, parallel to the light wave polarization, and equal to 2.62 ± 0.21 V/cm. We also obtain the relative sign of M 1 and E1. Using a theoretical value of E 1 and a well-defined phase convention, we deduce for the magnetic moment of the transition < 7S, 1/ 2 | μ z | 6S, 1/ 2 > = - (4.24 ± 0.34) 10-5 |μB|, in good agreement with a theoretical estimate. This result can also be expressed in terms of the oscillator strength in zero electric field f6S-7S = 4.05 × 10-15, or of the single-photon M1 decay rate Γ 7S-6S = 0.93 x 10-6 s-1.
We propose a new method to produce an electric and magnetic dipolar gas of ultracold dysprosium atoms. The pair of nearly degenerate energy levels of opposite parity, at 17513.33 cm^{-1} with electronic angular momentum J=10, and at 17514.50 cm^{-1} with J=9, can be mixed with an external electric field, thus inducing an electric dipole moment in the laboratory frame. For field amplitudes relevant to current-day experiments, i.e., an electric field of 5 kV/cm, we predict a large magnetic dipole moment up to 13 Bohr magnetons, and sizeable electric dipole moment up to 0.22 D. When a magnetic field is present, we show that the induced electric dipole moment is strongly dependent on the angle between the fields. The lifetime of the field-mixed levels is found in the millisecond range, thus allowing for suitable experimental detection and manipulation.
We have discovered an interference which results in the vanishing of some electric dipole transition amplitudes. A transition-matrix element T between certain S and P sublevels with the same value of MF vanishes when an applied magnetic field satisfies ${X}_{s}+{X}_{p}=\ensuremath{-}2{M}_{F}$, where $X={\ensuremath{\mu}}_{B}{g}_{J}\frac{B}{A}$, and A is the hfs constant. There must be an avoided crossing between the two states of the same MF which can only occur when one of the hyperfine manifolds has an inverted Zeeman effect. These conditions imply MF<0 and I>J. We observed the vanishing of T in 23Na for one of the $\ensuremath{\Delta}{M}_{F}=0$ optical transitions of the $3{S}_{\frac{1}{2}}(F=1)\ensuremath{\rightarrow}3{P}_{\frac{1}{2}}(F=1)$ manifold. Absorption of cw laser light was monitored by observing total fluorescence perpendicular to both the atomic and laser beams, and absorption vanished near an applied field of 155 G. T vanishes for a large number of cases including rf and microwave frequencies and is a rather general consequence of angular momentum selection rules and perturbation theory. This phenomenon may have application in optical pumping, Lamb-shift measurements, and atomic weak neutral-current experiments.
High angular momentum Rydberg states of atoms in strong magnetic fields or in strong magnetic and weak crossed electric fields correspond to classical regular drift trajectories around the positive ion core. The motion can be adiabatically separated in a fast cyclotron motion, an oscillation in magnetic field direction, and a slow drift motion. Some of the drift trajectories display huge electric-dipole moments induced by the weak electric field. Corresponding atomic drift states with large electric dipole moments are theoretically predicted. In the experiment drift states are excited by an optical one-photon transition. The excitation of drift-state atoms is very efficient in the vicinity of anti-crossings between Rydberg states with large photoexcitation cross section and drift states. The drift-state atoms are separated from other Rydberg atoms via electric-dipole deflection in an inhomogeneous electric field. The size of the observed dipole moments agrees quite well with theoretical values.