Temperature dependence of the line shapes of two-photon excited transitions in KMgF3 : Eu2+

The two-photon excitation line shapes of f-f transitions of Eu2+ in KMgF3 have been investigated as a function of temperature. Results for several transition lines of the P-6(J) and D-6(J) multiplets are presented in this work. The two-photon excited transitions appear as zero-phonon lines with a Lorentzian profile whose peak energy is shifted from the zero temperature position. The observed temperature dependence of the zero-phonon line shapes is ascribed to the elastic scattering of the electronic transitions among vibrational states via anharmonic coupling to a phonon mode of the lattice heat-bath. In those components of 4f(7) multiplets whose energies are not resonant with the 4f(6)5d broad excited state, a direct proportionality to the phonon occupation number of the coupled mode is found for the line-shapes and peak-positions temperature dependences

Applications of synchrotron radiation in defect and color center research

VUV synchrotron radiation in the energy interval between 4 and 100 eV has been widely used in the study of the optical properties of large gap insulators either pure or doped with various impurities such as heavy metals and rare earths. Besides the absorption and emission properties, important results such as photon multiplication and Auger-free luminescence have been revealed in these investigations. The radiative damage produced in ionic crystals by synchrotron radiation is also discussed, with a brief description of the lattice defects produced and the atom or ion desorption from the irradiated crystals. © 1990

Two-photon absorption of color centers in NaF

Two-photon absorption cross sections of the N1 and F3+ centers in NaF have been determined by means of the luminescence excited by the two-photon absorption. The measured polarization dependence of the process led us to attribute the excitation to the Ag→Ag transition in the N1 center and to the A→E transition in the F3+ center. © 1979 The American Physical Society

Picosecond spectroscopy of color center in KBr:OH-

The rapid decay of the excited state of the F centers in KBr:OH- has been measured by mean of a pump and probe technique with picosecond time resolution. The lifetime of the F centers (τ ~ 1 μs at 77 K) is shortened in the OH- doped samples, to τ ∼ 310 ps. The quenching of the normal radiative lifetime seems to be related to librational excitation of the OH- molecular ion. © 1993

Laser stimulated luminescence in KCl and NaF containing color centers

A broad luminescence band was found in laser irradiated KCl and NaF crystal containing color centers. This emission extends on both sides of the laser line and is interpreted as "hot" fluorescence due to radiative retrapping of laser ionized color centers. © 1977

On the lifetime of the I-4(13/2) emitting level of the Er3+ ions in phosphate glasses

The decay time of the I-4(13/2) --> I-4(15/2) transition of Er3+ ions in phosphate glasses has been measured through a variable frequency of the pump beam intensity. It has been found that the decay times depend upon temperature and upon the presence of Yb codoping of host glass. The room temperature decay time increases from 5 to 8ms in presence of Yb codoping, but the longer decay time seems to be independent of the relative amount of Er and Yb. The decay times increase at low temperature, where, however, careful control of the sample temperature heated by the pump beam has to be performed. Mechanism of radiative and non-radiative decays are briefly described

Segregation of thallium impurities in the growth of sodium bromide single crystals

The effective segregation coefficient of Thallium impurities in NaBr single crystals, grown from the melt with the Kyropoulos method, has been measured in different growing conditions and found to be keff = 0.0164. © 1977

Spectroscopy with synchrotron radiation

We describe the results of spectroscopic investigations performed on solid materials using synchrotron radiation at the italian synchrotron radiation facility PULS showing the importance of such a radiation. A perspective for future developments using a third generation storage ring is also briefly outlined

Two-photon spectroscopy in KBr:In+

Two-photon excitation spectrum of the A band luminescence has been measured in KBr:In+. The non-linear absorption cross-section, in agreement with the selection rules, indicates that the two-photon process is an indirect one allowed by phonons. The shape of the excitation spectrum reveals a new feature, not present in the one-photon spectrum, that may be interpreted as due to the forbidden 1A1g → 3A1u transition. © 1982