This paper summarizes a long series of experiments that have been done on Rydberg states of Rb. The basic experimental technique that has been used is atomic-beam laser spectroscopy which allows both low-resolution and high-resolution studies. Excitation of Rydberg states is provided by single-photon absorption from a suitably frequency-doubled rhodamine
6G tunable laser. Detection is done by field ionization and ion counting. These techniques have allowed us to study the critical ionizing field, which has been found to follow classical, hydrogenic behavior closely. Rydberg states of Rb have been observed from
n=28 up to
n>100. High-resolution spectroscopic studies have led to measurement of the fine structure for
np levels located between
n=28 and
n=60, as well as the isotope shift of the ground state, $\ensuremath{\delta}\ensuremath{\nu}=(172\ifmmode\pm\else\textpm\fi{}15)$ MHz. Anomalies in the intensity ratio of the doublet $5s\ensuremath{-}np$ transitions have been observed and interpreted as relativistic effects. Perturbations by weak and strong dc electric field are reported. In the case of weak electric fields it is possible to evaluate the polarizability. In the case of strong dc electric fields, new phenomena have been observed and analyzed. We also find experimental evidence of selective photoionization in the presence of an appropriate dc electric field, which could have some applications in laser isotope separation. Finally, we give the preliminary results of an experiment on the effect of a strong nonresonant electromagnetic field on high-lying Rydberg states.
The fine structure of high-angular-momentum
n=9 and 10 Rydberg states of barium has been measured precisely, using the resonant excitation Stark ionization spectroscopy method. Optical transitions corresponding to $(n,{n}^{\ensuremath{'}})=(10,30)$, (9,17), and (9,20) were induced with a Doppler-tuned
CO2 laser, determining the fine-structure energies corresponding to all
n=9 and 10 levels with $L\ensuremath{\geqslant}6$. The pattern of these fine-structure energies conforms closely with an effective potential model, by comparison with which the dipole and quadrupole polarizabilities of
Ba+ can be determined. Combining our data with earlier measurements made it possible to deduce, in addition, the portion of ${\ensuremath{\alpha}}_{2}$ due to the lowest excited
D state of
Ba+. Our best estimates of these three properties are ${\ensuremath{\alpha}}_{1}=124.30(16){a}_{0}^{3}$, ${\ensuremath{\alpha}}_{2}=2462(361){a}_{0}^{5}$, and ${\ensuremath{\alpha}}_{2}^{0}=1828(88){a}_{0}^{5}$.
A dramatic increase in studies of atoms in high Rydberg states has occurred in recent years. This increase derives in part from their many unusual physical properties and in part from recent technological advances, including the development of tunable dye lasers. This Resource Letter provides a guide to experimental work in this area and to the physics of Rydberg atoms. The letter E after an entry identifies introductory material or papers that can be readily understood by readers with no specialized knowledge of the field. The letter I indicates articles of a somewhat more specialized nature and the letter A identifies specialized papers written at an advanced level. An asterisk (*) indicates those articles to be included in an accompanying reprint book.
In this work radiative properties of neutral elements with one or two electrons outside closed subshells have been investigated. Using laser techniques in connection with atomic beams selective excitation of Rydberg states was performed. Most of the studied states were populated with two-step excitation. Some states were reached directly from the ground state or from a metastable state and occasionally two-photon absorption was used. The excitation sometimes involved the use of frequency-doubling and Raman- shifting techniques. By time-resolved detection of the decay light from an excited state, primarily information on the radiative lifetime is obtained. With two different experimental arrangements radiative lifetimes in several Rydberg states have been determined. Using the quantum-beat technique time-resolved detection also provides information on energy splittings. This technique was used to measure hyperfine-structure splittings.To obtain information about hyperfine-structure constants and isotope shifts high- resolution spectroscopy on a collimated atomic beam was also employed. The behaviour of highly excited alkali atoms is mostly hydrogen- like and well predicted by theory. Group III A elements have one electron outside a closed subshell and are expected to behave like alkali atoms. The situation is however complicated by the presence of doubly excited states. Configuration interaction can then cause a partial mixing between singly and doubly excited states. In the alkaline-earth atoms (group II A elements), having two electrons outside closed shells, the situation is similar. In a Rydberg series of one excited electron the admixture of doubly excited states can cause large deviations from hydrogenic behaviour. Another complication in the alkaline-earth atoms is the mixture of singlet- and triplet states. - 4 - The presented results from measurements made on Na, Mg, Ca, Sr, Ba, Al, Ga and In will primarily serve as a basis for tests of modern atomic-physics models. Some of the lifetime values are also of astrophysical interest. Keywords: Laser spectroscopy, Rydberg states, time resolved, high resolution, two-step excitation, metastable state, two-photon absorption, frequency doubling, Raman shifting, radiative lifetime, quantum beat, hyperfine structure, isotope shift, Stark shift, alkali atoms, group III A elements, alkaline-earth atoms, configuration interaction, singlet-triplet mixing.