Linear and nonlinear optical studies of CdS1−x Se x quantum dots

In this contribution we present and discuss our measurements on CdS_1?x Se _x quantum dots in a glass matrix. In linear absorption measurements we find the typical blue shift of the transitions with decreasing crystallite radius due to quantization. The luminescence shows a significant Stokes shift with respect to absorption, which is interpreted in terms of strong exciton-phonon coupling and allows to deduce the Huang-Rhys factor S. Under high excitation we find an additional emission band on the high energy side, which can be attributed to the recombination of an excited two electron-hole pair state to a one electron-hole pair state in agreement with theory. Pump and probe beam experiments give a bleaching but no hole burning. Finally we discuss some open questions especially concerning the high energy structures in the absorption spectrum.     

The quadrupole moment of the neutron-halo nucleus11Li

The quadrupole moment ratio of⁹Li and¹¹Li was measured by a combination of in-beam laser induced nuclear polarization and Β-NMR in LiNbO₃. The result ¦Q(¹¹Li)/Q(⁹Li)¦=1.14(16) is consistent with cluster models describing¹¹Li as composed of a⁹Li core and a far extended halo of two loosely bound neutrons.     

Measurement of nuclear moments and radii by collinear laser spectroscopy and by β-NMR spectroscopy

Experiments using laser spectroscopy and nuclear magnetic resonance techniques have been performed at ISOLDE on the unstable isotopes of several light elements. The results include nuclear ground state spins, magnetic dipole and electric quadrupole moments, and the behaviour of mean square nuclear charge radii within isotopic strings. These give important information about the nuclear structure at shell closures and close to the drip lines. This revised version was published online in July 2006 with corrections to the Cover Date.     

High-excitation photoluminescence studies of CdS1−x Se x quantum dots

Linear absorption and excitation dependent luminescence measurements on CdSSe quantum dots in glass are reported. The new aspects of the spectra are: (i) Stokes shift of linear emission versus absorption and (ii) appearance of new structures in the high energy wing of the luminescence peak under high excitation, which are interpreted as consequences of Coloumb effects, important for dot radii around the exciton Bohr radius.     

Glass ceramics — a laser host material

A report on the fluorescence and induced emission of Nd₂O₃ doped glass ceramics     

Optical polarization of neutron-rich sodium isotopes and β-NMR measurements of quadrupole moments

The nuclear quadrupole moments of neutron-rich sodium isotopes are being investigated with the help of in-beam polarization by optical pumping in combination with-NMR techniques. First measurements have yielded the quadrupole splittings of NMR signals in the lattice of LiNbO₃ for the isotopes²⁶Na,²⁷Na and²⁸Na. Interaction constants and ratios of the electric quadrupole moments are derived. In view of future experiments,-decay asymmetries for the sequence of isotopes up to theN=20 neutron shell closure,^26–31Na, have been measured.     

Measurement of the electric quadrupole moments of 26–29Na

The nuclear electric quadrupole moments of the isotopes ²⁶Na, ²⁷Na, ²⁸Na and ²⁹Na were measured by -NMR spectroscopy in single crystals of LiNbO₃ and NaNO₃. High degrees of nuclear polarization were produced by optical pumping of the sodium atoms in a fast beam with a collinear laser beam. The polarized nuclei were implanted into the crystals and NMR signals were observed in the -decay asymmetries. Preparatory measurements also yielded improved values for the magnetic moments of ^27-31Na and confirmed the spin I=3/2 for ³¹Na. The results are discussed in comparison with large-basis shell model calculations. Received: 1 February 2000 / Accepted: 3 April 2000