RAYLEIGH SCATTERING OF MÖSSBAUER γ-RAYS IN THE AMORPHOUS POLYMER POLYMETHYL METHACRYLATE

HAL Id: jpa-00219699

https://hal.archives-ouvertes.fr/jpa-00219699

Submitted on 1 Jan 1980

HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

RAYLEIGH SCATTERING OF MÖSSBAUER γ -RAYS IN THE AMORPHOUS POLYMER POLYMETHYL

METHACRYLATE

G. Albanese, A. Deriu, C. Ghezzi

To cite this version:

G. Albanese, A. Deriu, C. Ghezzi. RAYLEIGH SCATTERING OF MÖSSBAUER γ-RAYS IN THE

AMORPHOUS POLYMER POLYMETHYL METHACRYLATE. Journal de Physique Colloques,

1980, 41 (C1), pp.C1-133-C1-133. �10.1051/jphyscol:1980131�. �jpa-00219699�

JOURNAL DE PHYSIQUE Col10que C1, supplmenf au n O 1, Tome 41, janvier 1980, page C1-133

R A Y L E I W SCAllERING OF @SBAUER Y-RAYS I N THE AMORPHOUS POLYMER WLMulETHYL METHACRYLATE G. Albanese, A. Deriu and C. Ghezzi

+

I s k i t u t o d i Fisica d e l t 'lhiversita', Pamna, I t a l y . + Laboratorio Maspec deZ C. N. R., Pamna, ItaZy

.

Resume

-

L'effet MEssbauer a dte employd'pour sdparer la diffusion Rayleigh Blastique et non dlastique des rayons-Y de 14.4 KeV du ~e~~ dans le polymsre amorphe polym~thylmdthacrylate. La m&e mdthode ddcrite ailleurs /I/ a Btd employ6 pour sLparer les rayons-y diffuads dlastiquement par l'dchantillon de ceux qui ont subi une diffusion inglastique. Les deux intensitids, 1'6lastique et la non dlastique, mdsurdes en fonction de (sin O)/h

,

montrent que la diffusion non dlastique par les vibrations thermiques est une fraction considerable de 11intensit6 totale, mn&ne proche du premier maximum de diffraction.

La dependence de la temperature pour les intensites elastiques et inelastiques a It6 mesurg jusqu'au point de fusion. Une considerable rdduction de Iel et une consdquente croissance de Iin a dtE observde au del3 de la temperature de vetrification Tg. Ce rdsultat peut dtre d G a l'excitation, lorsque T > T g , de mouvements de libration des parties des chaines polymGriques; cette interpretation est en accord avec des resultats semblables obtenues dans d'autres verresorganiques /2,3/.

Un petit dlargissment de la distribution en energie des rayons-y diffractds a dtd observe tres proche du point de fusion. De ceux rdsultats on obtient un temp de relaxation T = 2.7.10-~ sec.

Abstract

-

The MEssbauer effect was used for measuring the elastic and inelastic Rayleigh scattering of the ~e~~ 14.4 KeV Y-rays in the amorphous polymer polymethyl methacrylate. The same procedure described elsewhere /I/ was used for separating the y-rays elastically scattered by the sample from those that undergo inelastic scattering. The observed dependence of the elastic and inelastic scattering intensi- ties on (sin @)/A indicate that the inelastic scattering by thermal vibrations is a considerable frac- tion of the total intensity just outside the first diffraction maximum.

The temperature dependence of both elastic and inelastic intensities has been measured up to the melting point. A strong decrease of Iel and a consequent increase of Xin was observed above the glass transi- tion temperature Tg. This behaviour may be attributed to the excitation at T > T g of librational motions of part of the polymeric chain in accordance with similar results in other organic glasses / 2 , 3 / .

A small broadening in the energy distribution of the diffracted y-rays was detected very near the mel- ting point. From this data a diffusion relaxation time T = 2.7.10-7 sec was deduced.

References

/1/ Albanese,G., Ghezzi, C., Merlini,A. and Pace,S., Phys.Rev.

E ,

(1972) 1746.

121 Champeney,D.C. and Sedgwick,D.F., 3-Phys. C

5

(1972) 1903.

131 Champeney,D.C. and Dean,G.W., J.Phys. C

8

⁽¹⁹⁷⁵⁾

1276.

An extended version of this abstract is in press in 11 Nuovo Cimento.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980131