New Method for Precision Lifetime Measurements by Laser Excitation of Fast-Moving Atoms

Abstract

A new method for precision measurements of atomic lifetimes by laser excitation of fast beams is described which is expected to allow accuracies of AT/T = 10" 3 . A first application to Ba + -6 2 -P 3 / 2 yields as a preliminary result T = 6.21 ±0.06 nsec.

High resolution spectroscopy of the transition 5d2D3/2?6p2P 3 2/0 in a fast Ba+ ion beam

“…On both lines laser experiments with fast ion beams have already been performed. The blue line was examined with regard to lifetime [9] and hfs [10,6] and the yellow line to lifetime [11] and g-values E7]. Our first fast barium ion beam laser experiment was performed with the Marburg separator MARS II on mass separated 137Ba.…”

Fast-beam-spectroscopy by combined gas cell-laser excitation for cascade-free lifetime measurements of highly excited states

“…The laser induced change of the population densities N, and N k can be described by the corresponding rate equations, which are given in the form (1) where W.k and A u are the transition probabilities of induced and spontaneous emission, g, and gk the statistical weights, z, and z k the spontaneous lifetimes of levels n and k, and C, and C k are the corresponding cascades from levels higher than the n-th one. Separately specified is that portion of cascades resulting from intermediate levels i with energies E,>E i >E k and therefore being influenced by the laser excitation 9 In general, this makes necessary to solve a system of n-k coupled differential equations with regard to additional rate equations of the levels k + 1 up to n-1.…”

“…The selective excitation of fast moving ions and atoms by laser radiation has been successfully demonstrated by several authors [1][2][3][4][5][6] and could be used together with time-of-flight measurements for high precision lifetime determinations of excited atomic levels. As opposed to a pure beam-foil experiment [7] this technique is not influenced by the serious problem of perturbing cascades, but takes advantage of all the unprecedented properties of fastbeam-spectroscopy [8].…”

Cascade-free lifetime measurements on the 1s3d-levels of He I

“…Therefore, experimental methods of determining lifetimes free from the effects of cascades are of particular interest. Only in favourable cases cascade-free lifetime measurements could be performed by combining impact excitation with a selective laser excitation [2,3] or by observing the exponential decay of quantum beats after foil excitation [4]. It was the aim of this work to develop a new experimental technique suitable for the observation of cascade-free Hanle-effect signals on fluorescence lines excited by impact excitation.…”