Radiative lifetimes of highly excited states in rubidium
2014 Measurements have been made of the natural radiative lifetimes of highly excited rubidium (9 ~ n ~ 18) S and D states. These results, as well as those already published concerning P and F states, agree well with the theoretical lifetimes calculated by the Bates-Damgaard method. J. Physique 41 (1980) 119-121 1 FTVRIER 1980, Classification Physics Abstracts 32.70 In the past few years, measurements of the radiative lifetimes of highly excited states of alkali atoms have been reported [1-3]. These results would clearly be of interest for physicists working in atomic physics, plasma physics, astrophysics. Moreover they allow interesting comparisons with theoretical calculations. We have already published measurements of the radiative lifetimes for some Rydberg P and F states in rubidium [4, 5]. In order to obtain a consistent set of lifetime values for a given alkali atom, we present here measurements concerning the nS and nD states of rubidium (9 n 18). Comparison is given between the obtained experimental values and the theoretical ones calculated by using a modified Bates-Damgaard Method [6, 7] (here after refered as B.D.). We use the classical method of time resolved laser induced fluorescence [4]. Rubidium atoms contained in a cell are excited in a given high-lying nS or nD state by stepwise pulsed excitation via the first resonant 5P state. For convenience the 5p3,2 state is chosen as the intermediate state for the excitation of the nS levels, the observation of the population decay being made on the nS -+ 5P 1/2 line. The nD states are produced by using light pulses whose wavelengths correspond either, to the 5PI/2 --+ nD3/2 transitions for n 13, or to the 5P3/2 -+ nD3/2,5/2 transitions for n &#x3E; 13; the population decay is observed on these same lines. Such a choice is determined by the fact that we are also interested in the study of some collisional properties of the nD states (results concerning the collisional properties of both the S and D levels will be published elsewhere [8]). Thus our reported lifetimes refer to the nD3/2 states for n 13 and to the nD states, without allowance for fine structure, for n &#x3E; 13. This is of no importance since the lifetimes corresponding to the two fine structure levels are expected to be very close, for a given n value. A high-speed photon counting system allows the determination of the decay of the excited.state population as a function of time for a given rubidium pressure. The extrapolation to zero rubidium pressure yields the natural radiative lifetime. The experimental set-up, shown in figure 1, has been already widely Fig. 1. Experimental set-up. Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphys:01980004102011900
Calculation of radial matrix elements and radiative lifetimes for highly excited states of alkali atoms using the Coulomb approximation
2014 Radial matrix elements have been computed involving highly excited states of alkali atoms. An entirely analytical Coulomb method has been used. Particular attention has been paid in the choice of the cut criterion. The extensive data are available from the author upon request and can be used to compute, for example, oscillator strengths, radiative lifetimes, branching ratios and polarizabilities of alkali Rydberg states. In order to test the results, radiative lifetimes have been derived for highly excited (10 ~ n ~ 28), S, P, D and F states of alkali atoms. The computed lifetimes are reported and are observed to be in good agreement with the available experimental data. LE JOURNAL DE PHYSIQUE TOME 40, MAI 1979, Classification Physics Abstracts 32.70
Archaeology and mud wall decay in a West African village
Abstract A detailed study of the processes of deterioration of mud walls and of the physical evolution and devolution of a contemporary West African village is seen to facilitate the location of decayed mud structures at a nearby archaeological site. Various climatic and pedological conditions at the site make it unlikely that such walls will be discerned. The archaeologist wishing to obtain the fullest and least biased picture of the settlement configuration of the ancient community should therefore heed all the inferential lessons to be had from a focused ethnographic investigation. Given similar climatic situations and practices of house construction, taphonomy and ethnographic analogies may both be necessary for a valid reconstruction of an archaeological settlement.