Temperature Dependence Of Fluorescence Lifetime Research Articles

Viscosity and temperature dependence of fluorescence lifetimes of anthracene and 9-methylanthracene

Time-correlated single-photon counting is used to determine the fluorescence lifetimes of anthracene and 9-methylanthracene over the temperature range 20-55°C as solutes in a variety of hydrocarbon solvents covering the viscosity range 0.3-200 cP (1 cP = 10-3 N s m-2). The absorption and emission spectra of both molecules show only small changes (e.g., 50 cm-1 shift in the absorption maxima) over this range of conditions. For anthracene, the fluorescence lifetime decreases with viscosity from a low viscosity limit; for 9-methylanthracene the fluorescence lifetime increases with viscosity and approaches a high viscosity limit. These results are quantitatively interpreted by a general kinetic scheme wherein rate coefficients are dominated by Franck-Condon factors in two types of coordinates: those of small groups such as H atoms where the dynamics are solvent independent, and those of larger groups where the rate is inversely proportional to the viscosity. The temperature dependence of the rate coefficients so obtained enables one to assign the spin multiplicity and energy of intersection (with the fluorescing state) of some of the states involved in the dynamics.

Temperature dependence of fluorescence lifetimes of 8-anilino-1-naphthalene sulfonate and solvent isotope effect

Deactivation of excited 8-anilino-1-naphthalene sulfonate in pronotated and deuterated solvents is investigated by the temperature dependence of fluorescence lifetimes. Results show that electron transfer from the S 1 excited state to the surrounding media is coupled with intramolecular vibrations of the solvent, particularly O-H or O-D deformation modes.

Temperature dependence of fluorescence lifetimes of trans-stilbene

The temperature dependence of the fluorescence lifetimes of trans-stilbene was measured with a picosecond laser and a streak camera. A smooth sigmoidal relation was obtained, quite similar to the temperature dependence of fluorescence quantum yields. The results have clearly shown that the radiative rate is essentially constant in the temperature range from 77 K to 295 K.

Emission cross section and fluorescence efficiency of Nd-pentaphosphate

The room-temperature cross sections for the Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F_{3/2}</tex> levels to the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{11/2}</tex> and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{9/2}</tex> manifolds (lower laser state and ground state, respectively) in NdP <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</inf> are measured by two spectroscopic methods. A value for the largest cross section of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sigma(R_{1} - Y_{2}) = 1.7 \times 10^{-19}</tex> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> is found. The highest effective cross section, resulting from superposition of two lines at 1.051 μm, gives a laser gain per Nd ion which is about 2/3 of the maximum gain in YAG:Nd. The relative branching ratio into the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{11/2}</tex> and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{9/2}</tex> manifolds is 0.65:0.35. Comparison of the integrated cross sections with the measured lifetime for 1-percent Nd in LaP <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</inf> indicates a combined efficiency <0.1 for the remaining transitions, namely radiative decay into the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{13/2}</tex> and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I_{15/2}</tex> manifolds and multiphonon quenching. A measurement of temperature dependence of fluorescence lifetime supports this last result.

Fluorescence quenching of the 4F3/2 state in Nd-doped yttrium aluminum garnet (YAG) by multiphonon relaxation

Quenching of the fluorescence from the 4F3/2 state (upper state of 1.06-μm laser transition) of YAG : Nd by multiphonon relaxation is investigated. Measurements of the temperature dependence of fluorescence lifetime and relative fluorescence efficiency are compared with an established model for multiphonon processes. An upper limit of 0.2 and a most probable value of 0.02 are obtained for the room-temperature efficiency of this quenching process.