On the theory of multiphonon relaxation rates in solids

1995 ◽  
Vol 103 (4) ◽  
pp. 1533-1543 ◽  
Author(s):  
S. A. Egorov ◽  
J. L. Skinner
Keyword(s):  
Relaxation Rates ◽  
Multiphonon Relaxation

Saturation effect on multiphonon relaxation rates

1998 ◽  
Vol 275-277 ◽  
pp. 430-434 ◽  
Author(s):  
F. Pellé ◽  
N. Gardant ◽  
F. Auzel ◽  
Groupe d'Optique des Terres Rares
Keyword(s):  
Saturation Effect ◽  
Relaxation Rates ◽  
Multiphonon Relaxation

Enhancement of the 1.31-μm emission properties of Dy3+-doped Ge–Ga–S glasses with the addition of alkali halides

2001 ◽  
Vol 16 (5) ◽  
pp. 1318-1324 ◽  
Author(s):  
Yong Beom Shin ◽  
Jong Heo ◽  
Hyoun Soo Kim
Keyword(s):  
Raman Spectra ◽  
Emission Intensity ◽  
Alkali Halide ◽  
Fiber Optic ◽  
Alkali Halides ◽  
Local Environment ◽  
Relaxation Rates ◽  
Multiphonon Relaxation ◽  
Emission Properties ◽  
Emission Level

Alkali halides such as KBr, KI, CsBr, and CsI were added to Dy3+-doped Ge–Ga–S glasses, and their effects on the 1.31-μm emission property were investigated. The intensities of the 1.31-μm emission (6F11/2 · 6H9/2 → 6H15/2) increased at the expense of the 1.75-μm emission intensity (6H11/2 → 6H15/2) with the alkali halide addition. The lifetimes of the 1.31-μm emission level also increased as much as 35 times from 38 μs for Ge–Ga–S glass to 1320 μs for the glass containing 10 mol% CsBr. These enhancements occurred only when the ratio of MX (M = K, Cs; X = Br, I)/Ga was equal to or larger than unity. Raman spectra of Ge–Ga–S–CsBr glasses indicated the formation of [GaS3/2Br]− complexes, which provide the preferred sites for Dy3+. Due to this new local environment of Dy3+, the multiphonon relaxation rates from the Dy3+:6F11/2 · 6H9/2 level decreased by approximately four orders of magnitude. The enhancement in the 1.31-μm emission properties with alkali halide addition supports the potentials of these glasses as hosts for the Dy3+-doped fiber-optic amplifiers.

Quantitative determination of longitudinal and transverse cross-relaxation rates

1999 ◽  
Vol 96 (9/10) ◽  
pp. 1608-1615
Author(s):  
T. E. Malliavin ◽  
H. Desvaux ◽  
M. A. Delsuc
Keyword(s):  
Quantitative Determination ◽  
Cross Relaxation ◽  
Relaxation Rates

Improved Contrast in Ultra-Low-Field MRI with Time-Dependent Bipolar Prepolarizing Fields: Theory and NMR Demonstrations

2013 ◽  
Vol 20 (3) ◽  
pp. 327-336 ◽  
Author(s):  
Jaakko O. Nieminen ◽  
Jens Voigt ◽  
Stefan Hartwig ◽  
Hans Jürgen Scheer ◽  
Martin Burghoff ◽  
...  
Keyword(s):  
Field Strength ◽  
Time Course ◽  
Signal Strength ◽  
Relaxation Rates ◽  
Resonance Imaging ◽  
New Approach ◽  
Spin Lattice ◽  
Low Field ◽  
Low Field Mri ◽  
Magnetic Resonance Imaging Mri

Abstract The spin-lattice (T1) relaxation rates of materials depend on the strength of the external magnetic field in which the relaxation occurs. This T1 dispersion has been suggested to offer a means to discriminate between healthy and cancerous tissue by performing magnetic resonance imaging (MRI) at low magnetic fields. In prepolarized ultra-low-field (ULF) MRI, spin precession is detected in fields of the order of 10-100 μT. To increase the signal strength, the sample is first magnetized with a relatively strong polarizing field. Typically, the polarizing field is kept constant during the polarization period. However, in ULF MRI, the polarizing-field strength can be easily varied to produce a desired time course. This paper describes how a novel variation of the polarizing-field strength and duration can optimize the contrast between two types of tissue having different T1 relaxation dispersions. In addition, NMR experiments showing that the principle works in practice are presented. The described procedure may become a key component for a promising new approach of MRI at ultra-low fields

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