Neodymium, fluorescent decay

Geusic et al. (118) made measurements of the fluorescent lifetime of neodymium in yttrium aluminum garnet (Y3A15012). For neodymium concentrations up to 3 atomic per cent, the measured fluorescent-decay time is approximately 200 jtxsec at both IT and 300°K. Above 6 atomic per cent, a marked decrease in the fluorescent lifetime is observed. They suggest that this is due to neodymium interactions. It is to be noted that yttrium aluminum garnet is a laser material of very exceptional quality. 

Maurer (129) examined the fluorescent decay of neodymium in a number of glass hosts. The results of his study at 300°K are ... 

Hirayama and Lewis (131) studied the fluorescent decay of the 3/2 state of neodymium in a very large number of alkali silicate and alkali germanate glasses. Data were taken by exciting a flat sample with a xenon... 

To a very large extent, most of the recent data on fluorescent decay times of the other trivalent ions (those beside terbium, neodymium, and europium) stems in some way from laser experiments. In this section some representative data on these are considered. 

Hoskins and Soffer (117) measured the fluorescent lifetime of the neodymium 4Fy2 state in yttrium oxide. They found a value of approximately 260 /zsec both at room temperature and at liquid-nitrogen temperature. They also observed a weaker long-lived component in the decay. They were unable to say whether this was evidence for a low-transition-probability ion site, or an effect of trapping of the resonance radiation near 0.9 /x. They report laser action, with a threshold of 260joules. This is a fairly high value for most crystalline materials. 

The decay of the chromium fluorescence around 7356 A (the 2E level) involves a sum of exponentials. The longest decay time is 46 msec at room temperature and is associated with the R line. The presence of neodymium does not produce any significant change in the lifetime of the R line. 

His experiments were primarily upon a single soda-lime silicate, which was chosen because it had been studied extensively in the literature and can be made in small amounts with fair optical quality. The decay for this glass with 0.8 per cent Nd203 added is shown in Fig. 33. It is quite clearly not a single exponential. One finds that the slope changes by a factor of three over the range examined and that the curvature increases with neodymium concentration. The measurements made at long times were done with a mechanical shutter that shielded the photomultiplier tube from the initial intense fluorescence. When this was not done, hysteresis in the photomultiplier tube led to spurious results. 

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