| The use of energy transfer is important for improving the efficiency of neodymium lasers since the strongly forbidden neodymium f-f transitions make excitation to upper electronic states difficult and inefficient. Excitation of the strongly absorbing f-d transition of Ce('3+) followed by energy transfer to Nd('3+) can increase the population of excited Nd ions. In this study Ce('3+) and Nd('3+) luminescence and energy transfer properties in ionic lanthanide crystals have been studied.;The measured excitation spectrum of cerium consists of a broad, structureless band with peak at 300 nm. The emission spectrum consists of a band with peak at 335 nm and a higher energy shoulder at 320 nm.;Cerium decay from Ce pentaphosphate crystals, Ce(,x)La(,1-x)P(,5)O(,14), following pulsed excitation at wavelengths from 282 to 299 nm follows single exponential kinetics characterized by a 22 (+OR-) 2 nsec lifetime. This lifetime is independent of the cerium mole fraction for 0.2 < x(,Ce) < 1.0, crystal temperature from 25 to 180(DEGREES)C, crystal size from 36 microns to 1 mm, presence of crystal twin planes, or crystal orientation relative to the excitation beam. For Ce(,y)La(,1-y)Na(SO(,4))(,2)H(,2)O, the cerium luminescence kinetics are characterized by single exponential decay with a 20.8 (+OR-) 0.8 nsec lifetime at 77 and 298 K for 0.0005 < y < 1.0. Ce luminescence decay kinetics from aqueous cerous sulfate solution are also found to be independent of Ce('3+) concentration. Ce decay follows single exponential kinetics characterized by a 40 (+OR-) 2.2 nsec lifetime for solutions 0.2800, 0.0467, and 0.0078 molar in cerous ion.;An excitation band at 300 nm corresponding to Ce('3+) absorption followed by Ce-to-Nd energy transfer is observed in pentaphosphate and sodium sulfate crystals containing Ce('3+) and Nd('3+) when Nd('3+) luminescence at 870 nm is monitored. In Ce(,0.5)Nd(,0.5)P(,5)O(,14) crystals, the Ce('3+) lifetime is shortened to 3.8 (+OR-) 0.4 nsec as result of non-radiative energy transfer to the Nd('3+) ions. In the Ce-Nd sodium sulfate crystals, the energy transfer efficiency is greater than 0.90 for x(,Nd) greater than 0.50. The cerium decay kinetics from Ce-Nd sodium sulfate crystals are non-exponential and can be fit to a multipole interaction model with dipole-dipole interaction as the dominant term. The rate of Ce-to-Nd energy transfer has a second-order dependence on the Nd mole fraction and a zero-order dependence on the Ce mole fraction.;An investigation of the factors necessary for characterizing the energy transfer process, such as Ce-to-Nd energy transfer efficiencies and mechanism, Ce and Nd concentration dependences, and the concentration dependence of Nd luminescence is reported in this study for two lanthanide crystals: lanthanide pentaphosphate, LnP(,5)O(,14), and lanthanide sodium sulfate, LnNa(SO(,4))(,2)H(,2)O. These materials contain lanthanide ions as a stoichiometric component, rather than as a dopant.;For Nd(,.10)La(,.90)Na(SO(,4))(,2)H(,2)O at room temperature, neodymium decays with nearly single exponential kinetics characterized by a 90-microsecond lifetime; for Nd(,.50)Ln(,.50)Na(SO(,4))(,2)H(,2)O the Nd lifetime is 15 microseconds. Thus, concentration quenching is efficient. The presence of cerium also decreases the Nd luminescence lifetime. The intensity of Nd luminescence due to Ce excitation followed by Ce-to-Nd energy transfer to Ce-Nd sodium sulfates depends in a complex manner on the Ce and Nd mole fraction.;Holmium erbium in crystals of Ho(,y)Ce(,1-y)Na(SO(,4))(,2)H(,2)O and Er(,y)Ce(,1-y)Na(SO(,4))(,2)H(,2)O quench cerium luminescence, but do not show any luminescence due to cerium absorption and energy transfer. The quenching rate, which is the same at 77 and 298 K, is first-order in the holmium and erbium mole fractions. |
