CdS 0.65 Se 0.35 nanoparticles are grown in a glass matrix by thermally annealing a base glass material, in which Cd, S, and Se were introduced by diffusion. The starting base material contains no crystalline structure. A comparative study of the confinement effects on the annealed samples using photoluminescence, low-frequency Raman, and optical Raman scattering experiments is presented. Growth of nanoparticles is observed with the three independent experimental techniques as the annealing temperature is varied from 550 to 800 °C. Radii of the thermally grown nanoparticles calculated from the three independent techniques are found to be in good agreement. In addition, surface phonon modes are observed in the optical spectral range, the frequencies of which agree well with those calculated theoretically. As expected from the theory, the positions of the surface phonons are found to be independent of the particle size.
Precision measurements are made of the second order Doppler shift and absorption areas of the Mossbauer line of ll9Sn, present as a dilute impurity in palladium lattice, over a range from liquid helium temperature to about 750 O K . The weighted mean temperatures have been determined from the moments w ( -2 ) , w ( -l), w ( + l), and w( + 2 ) of the phonon frequency distribution in the palladium lattice as seen by the Mossbauer l19Sn impurity atoms. Assuming a Debye spectrum, ratios of the impurity-host t o host-host spring force constants have been estimated from the characteristic temperatures on the basis of Mannheim's model of nearest neighbour central forces. The Sn-Pd force constant has been found weaker than the equivalent Pd-Pd force constant indicating the presence of resonance band modes without any evidence of localised impurity modes.Es werden Prlzisionsmessungen der Doppler-Verschiebung zweiter Ordnung und der Absorptionsflachen der MoDbauerlinie von ll9Sn, das als verdunnte Storstelle im Palladiumgitter vorliegt, im weiten Temperaturbereich vom flussigen Helium bis etwa 750 O K durchgefuhrt. Die gewichteten mittleren Temperaturen werden aus den Momenten w ( -2 ) , w ( -l), w ( + l ) und w ( + 2 ) der Verteilung der Phononenfrequenzen im Palladiumgitter bestimmt, die auf die 119Sn-Mol3bauerstorstellen einwirken. Unter der Annahme eines DebyeSpektrums werden die Verhaltnisse der Storstellen-Wirtsgitter-zu den Wirtsgitter-Wirtsgitter-Federkonstanten aus den charakteristischen Temperaturen auf der Basis des Modells yon Mannheim fur die Zentralkrafte der iiachsten Nachbarn berechnet. Es wird gefunden, daD die Sn-Pd-Kraftkonstante schwacher als die aquivalente Pd-Pd-Kraftkonstante ist, was die Anwesenheit von Resonanzmoden anzeigt, ohne irgendeinen Hinweis auf lokalisierte Storstellenmoden.
Ratios of impurity-host to host-host spring force constants are computed from the temperature variation of recoilfree fraction and second order Doppler shift of Mossbauer Sn119 atoms present as dilute impurity in hosts of various masses. der MoSbauer-Storst~ellenatome in verschiedenen Wirtsmatrizen werden atis der TemperaturLnderung des ruckstol3freieii Anteils und der Dopplerverschiebung zweiter Ordnung berechnet,. Derartige Berechnungen der h d e r u n g der Kraftkonstante fur verschiedene Storstellen-WirtsSysteme werden auf der Grundlage eines Zeritralkraftmodells nachster Nachbarn durchgefuhrt, wobei ein Debye-Spektrum angenommcn mird nnd eine relative Wichtung von Resonanz-und lokalisierten Schwingungsmoden beriicksiehtigt wird. Die berechneten Ergebnisse werden im Hinblick auf den EinflulJ von Temperatur-, Massen-und Kraftkonst,anten-Anderung auf die 3168-bauerparameter diskutiert.
I . IntroductionWhen the Mijsshaner nucleus is present as a dilute inipurity in a metallic host of non-resonant atoms in the form of a solidsolution, theMosshaiier parameters influenced by the dpnarnical hehaviour of the inipnrity are also affected by the change in the iiia~s a t the defect site and changes in the force constants in the vicinity. I t affects the mean square aniplitude and velocity of impurity nuclei in the host lattice which produce a corresponding change in the Miissbauer recoilfree fraction and the secondordrr Doppler shift. The t,eniperatiirc variation of these parameters yields the weighted niean temperature of the inipiirity atom. [5] who c~ilculated expressions for the Debye-Waller factor for an isolated impurity, which mas evaluated in the limit of large impurity mass. These authors have used a niodel for the crystal which is inconsistent with Sewton's third law [l] and their results for the l) New Delhi, 110029, India.
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