Abstract
We have measured the radiative efficiency (ratio of -line photons to the total number of photons emitted) and absorption cross sections for the lines of dilute ruby, as a function of polarization and temperature between 20 and 373°K. We have also measured the fluorescent lifetime from 20 to 373°K in optically thin crystals, and from 20 to 273°K in optically thick crystals. The difference between the reciprocal lifetimes in thin and thick crystals is directly comparable (via the Einstein relations) with the integrated absorption in the lines. This comparison shows that for the lines at 20 and 77°K detailed balance holds to well within the experimental error of 5%, a precision never to our knowledge previously approached in solids. An upper limit of 0.002 was placed on any Stokes shift of the line, confirming that it is a no-phonon line. Comparison of and spectra confirms that the lines and their vibronic satellites are predominately electric-dipole in character. The radiative efficiency of the lines is strongly polarization dependent, a result which differs from that of previous workers. Its temperature dependence agrees well with that calculated from the observed vibronic spectrum at 77°K. The integrated absorption in the lines increases by about 20% between 20 and 373°K. The absorption in the vibronic satellites on the high-frequency side of the lines appears to be weaker than the corresponding emission on the low-frequency side. The temperature variation of the lifetime agrees well with that calculated from the absorption and radiative efficiency, but about 10% of the decay at 77°K and 30% at 373°K is either nonradiative or by emission at wavelengths outside the range of observation. The implications of our results for laser work are discussed.
- Received 1 September 1964
DOI:https://doi.org/10.1103/PhysRev.137.A1117
©1965 American Physical Society