Search

A sensitive method to study a dilute ultracold plasma based on the autoionization resonances of Rydberg atoms is demonstrated. Ultracold 40Ca Rydberg atoms are prepared in a continuously operating magneto-optical trap. A method that allows the detection of the plasma with ion and electron densities below 109 m–3 is shown. Experimental studies of resonances at the two-photon Rydberg transition have been carried out using 672 and 798 nm resonant laser beams. The autoionization resonance is observed during fluorescence of single-charged 40Ca ions at a wavelength of 397 nm. The dependence of the amplitude of autoionization resonance on the density of ions in the continuously generated ultracold plasma is obtained. [ABSTRACT FROM AUTHOR]

Two-photon spectroscopy has been applied to measure the Rydberg transition energies in the n1S0 state of 40Ca atoms at n = 40–120. The ionization potential determined from these experimental data is 49305.91966(4) cm−1. Using the frequency-doubled radiation and fundamental radiation from a diode laser, the frequencies of two-photon transitions to Rydberg states with the principal quantum numbers of 75 and 76 have been measured simultaneously with the frequencies of resonances of saturated absorption in a rubidium vapor cell. The chosen transition frequencies for rubidium atoms are known with high accuracy. Such frequency references make it possible to improve the accuracy of determination of the Rydberg transition energies in 40Ca atoms. [ABSTRACT FROM AUTHOR]

The spectra of highly excited 40Ca atoms prepared using a magneto-optical trap and an ultraviolet laser are experimentally studied. The dependence of the atomic density in the magneto-optical trap on the detuning frequency of cooling radiation and on the magnetic field gradient is determined. By using the technique based on the reduction of resonance fluorescence, the energy of the 761S0 Rydberg state for 40Ca atoms is determined. A new scheme for stabilization of the laser frequency to create highly excited Rydberg atoms is demonstrated. This scheme employs the saturated absorption spectrum in a cell with rubidium atomic gas. [ABSTRACT FROM AUTHOR]

In a magneto-optical trap (MOT) of Li, two-photon Rydberg resonances are recorded by using a spectroscopic technique, which based on variation in the resonance fluorescence. The first excitation frequency is detuned by 0.59 GHz from the intermediate 2 P state. Two counter-propagating laser beams are used. The resonances are studied on two-photon transitions 2 S − nl in a range of principal quantum number n from 38 to 120. The widths of the observed resonances are varied from 4.4 to 13 MHz for different MOT parameters. [ABSTRACT FROM AUTHOR]

We study power broadening of coherent two-photon resonances on Rydberg transitions in lithium-7 atoms in a magneto-optical trap (MOT). We apply the spectroscopic technique based on the reduction of resonance fluorescence in the MOT. One of the main contributions to the spectral broadening is associated with heating of the trapped atoms by laser cooling beams. We suggest a new nondestructive method to measure the atomic temperature in a working MOT using two-photon spectroscopy with variable directions of probe beams. [ABSTRACT FROM AUTHOR]

A study of the optical spectra of ultracold highly excited Li7 atoms has revealed coherent and non-coherent components of two-photon excitation. The high sensitivity of the method makes it possible to record pure coherent resonances at a detuning of 803.5 MHz from the intermediate 2 P resonance. [ABSTRACT FROM AUTHOR]

Forbidden 2 P- nP and 2 P- nF transitions in the ranges of the principal quantum number n = 42-114 and n = 38-48 have been detected in the optical spectra of ultracold highly excited lithium-7 atoms. The presence of forbidden transitions is due to induced external electric fields. The quantum defects and ionization energy obtained in various experiments and predicted theoretically have been discussed. [ABSTRACT FROM AUTHOR]

The spectra of excited lithium-7 atoms prepared in a magneto-optical trap are studied using a UV laser. The laser diagnostics of the energy of Rydberg atoms is developed based on measurements of the change in resonance fluorescence intensity of ultracold atoms as the exciting UV radiation frequency passes through the Rydberg transition frequency. The energies of various nS configurations are obtained in a broad range of the principal quantum number n from 38 to 165. The values of the quantum defect and ionization energy obtained in experiments and predicted theoretically are discussed. [ABSTRACT FROM AUTHOR]

We describe our experimental technique for preparation and study of ultracold gas of Rydberg atoms. A magneto-optical trap for 7Li atoms is assembled. Using an ultraviolet laser, we perform a cw two-step excitation of atoms in the ground state to highly-excited states. For identification of highly-excited Rydberg states ( n = 41 and 110), we record the resonance fluorescence of ultra-cold atoms in the trap. [ABSTRACT FROM AUTHOR]

This work is aimed at preparing highly excited optically cooled lithium-7 atoms for producing a strongly nonideal plasma and Rydberg matter. A setup implementing a novel nondestructive technique for preparation and diagnostics of highly excited Rydberg atomic states is constructed. The operation of this setup is based on the usage of a cw high-power ultraviolet laser combined with a magneto-optical trap. The diagnostics of highly excited states is performed by the direct recording of the variations in the fluorescence of ultracold lithium-7 atoms in the magneto-optical trap. [ABSTRACT FROM AUTHOR]

This study is aimed at obtaining high concentration of optically cooled lithium-7 atoms for preparing strongly interacting ultracold plasma and Rydberg matter. A special setup has been constructed, in which two high-power semiconductor lasers are used to cool lithium-7 atoms in a magneto-optical trap. At an optimum detuning of the cooling laser frequency and a magnetic field gradient of 35 G/cm, the concentration of ultracold lithium-7 atoms reaches about 10 cm. Additional independent information about the concentration and number of ultracold lithium-7 atoms on different sublevels of the ground state was obtained by using of an additional probing laser. [ABSTRACT FROM AUTHOR]

A setup for laser cooling and confining of Li atoms in a magneto-optical trap has been built. The possibility of cooling and trapping of Li atoms in a wide range of frequency detuning of the cooling laser has been proved experimentally. Independent information on the density and number of ultracold Li atoms on various ground-state sublevels, as well as on the temperature of the atoms, has been obtained with the use of a probing tunable laser. This information is important for preparing an ultracold plasma and Rydberg matter. [ABSTRACT FROM AUTHOR]