A method for measuring cascade-free mean lives

The measurement of lifetimes in atoms, molecules and ions

“…It was proposed as a suitable method for lifetimes in atoms and molecules by Brannen et aZ(1955) and was used by them to obtain the value 11.2 k 0.2 ns for the lifetime of the 73S1 state of mercury. The method has since been used by Pardies (1968) and Camhy-Val and Dumont (1970) to measure this same lifetime in mercury, by Kaul (1966), Nussbaum andPipkin (1967) and Popp et aZ(l970) to measure the lifetime of the 63P1 level of mercury, by Camhy-Val, Dumont and co-workers (Camhy-Val and Dumont 1968b, Camhy-Val et a1 1969b, Dumont et aZ 1970 to measure five lifetimes in Ar 11, by Masterson and Stoner (1973) to measure the lifetime of the 3d' 2G7,2,9,8 levels in 0 11, and by Yamagishi and Inaba (1974) to measure the lifetimes of the 2pg and 2pg levels in Ne I, but these experiments (with the exception of that of Popp et aZ(l970)) have suffered from either a poor statistical accuracy or (in the case of the experiments of Camhy-Val, Dumont and co-workers) a high source pressure (of the order of 0.1 Torr or higher) and consequent possible systematic errors from radiation trapping and collisional de-excitation (see 991.3 and 5.6.1). It is only following the more recent work of Holt and Pipkin (1974) on the lifetime of the 73s1 level of Hg, of King et aZ(1975b) on the lifetime of the a 3&+ state of Hz, and of King et a2 (1976) on the lifetime of the 4p *D;iz level of Ar II that the full potential of the photon-photon coincidence method has become apparent.…”

“…This is particularly true with heavy ions, high charge states and high beam velocities as the fraction of ions that are initially aligned decreases rapidly with these parameters. Masterson and Stoner (1973) reported an experiment in which the lifetime of an intermediate state was measured by counting correlated photons from decays into and out of this level (such 'photon-photon' coincidence experiments are discussed more fully in $6.1). Because of the high velocity of the emitters, the experiment had to be repeated for several distances between the two detectors.…”

Comments on Foil Effects in Beam-Foil Mean-Life Measurements

“…In photon-photon coincidence techniques which have recently been applied to the beam-foil source [9], time-dependent scattering can cause a relative change in the probability of detecting the emitted photon downstream. The detection probability will therefore be time dependent and the mean life will be affected by changes in foil parameters.…”

Recent Progress in Studies of Atomic Spectra and Transition Probabilities by Beam-foil Spectroscopy

“…Until a few years ago it was assumed that the counting rates would not be sufficient and that random coincidences would thus dominate the data. Recently, important experimental improvements have been developed by Masterson and Stoner [99], and now such measurements appear as quite realistic.…”