HAL Id: jpa-00216951
https://hal.archives-ouvertes.fr/jpa-00216951
Submitted on 1 Jan 1976
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.
DYNAMICS OF PHOTO-INDUCED SILVER COLLOID FORMATION IN SILVER HALIDE
MICROCRYSTALS
C. Marquardt, J. Giuliani, R. Williams
To cite this version:
C. Marquardt, J. Giuliani, R. Williams. DYNAMICS OF PHOTO-INDUCED SILVER COLLOID
FORMATION IN SILVER HALIDE MICROCRYSTALS. Journal de Physique Colloques, 1976, 37
(C7), pp.C7-400-C7-400. �10.1051/jphyscol:1976791�. �jpa-00216951�
C7-400 JOURNAL DE PHYSIQUE Colloque CI, supplement au n° 12, Tome 37, Decembre 1976
DYNAMICS OF PHOTO-INDUCED SILVER COLLOID FORMATION IN SILVER HALIDE MICROCRYSTALS
C. L. M A R Q U A R D T , J. F . G I U L I A N I a n d R. T. W I L L I A M S U . S. Naval Research L a b o r a t o r y Washington, D . C. 20375, U . S. A .
Résumé. — La spectroscopie de transmission optique (300-1 000 nm) résolue dans le temps a été utilisée en conjonction avec les mesures d'absorption optique à l'état statique et de RPE pour observer le développement du colloïde d'argent dans les microcristaux d'halogénures d'argent à la suite d'une excitation optique. Les microcristaux d'halogénures d'argent (de taille ~ 100 A) ont été obtenus comme une phase séparée dans un verre photochrome. En utilisant la deuxième harmonique d'un laser déclenché à rubis pour l'excitation optique, le spectre de transmission résolu dans le temps a été obtenu par un spectromètre vidicon ainsi que par mesures monochro- matiques d'ondes diverses. Le colloïde d'argent a été identifié par sa bande d'absorption optique bien connue d'environ 580 nm. On a trouvé qu'à 300 K la formation du colloïde a suivi un accrois- sement exponentiel simple ayant un temps de croissance d'approximativement 7 us. Ce comporte- ment est indépendant de la température entre 300 K et 150 K, mais la formation des colloïdes a cessé subitement entre 150 K et 130 K. A 130 K et au-dessous aucun colloïde n'a été détecté. Ces résultats sont consistants avec un mécanisme de croissance de colloïdes suggéré par des précédents calculs d'orbitales moléculaires [1]. De plus ces résultats indiquent que les ions Ag+ qui contribuent à la formation des colloïdes sont des ions mobiles de surface (surfaces internes ou externes) plutôt que des interstitiels de masse.
Abstract. — Time-resolved optical transmission spectroscopy (300-1000 nm) has been used in conjunction with steady state optical absorption and ESR measurements to observe the growth of colloidal silver in silver halide crystallites following optical excitation. The silver halide crystal- lites ( ~ 100 A in size) were obtained as a separated phase in a photochromic glass. Using the fre- quency-doubled output of a Q-switched ruby laser for optical excitation, time-resolved transmis- sion spectra were obtained with a vidicon spectrometer as well as by monochromatic measurements at various wavelengths. Silver colloid was identified by its well-known absorption band around 580 nm. It was found that at 300 K colloid formation followed a single exponential growth charac- teristic having a growth time of approximately 7 us. This growth characteristic was found to be independent of temperature between 300 K and 150 K, but colloid formation ceased rather abrup tly between 150 K and 130 K, below which temperature no colloid was detected. These results are con- sistent with a mechanism of colloid growth suggested by previous molecular orbital calculations [1].
Furthermore they indicate that the Ag+ ions which contribute to colloid formation are mobile surface ions (internal or external surfaces) rather than bulk interstitials.
Reference
[1] BAETZOLD, R. C, Phot. Sci. Eng. 19 (1975) 11.
D I S C U S S I O N R. J. F R I A U F . — T w o brief comments : In AgCl the
migration enthalpy for t h e collision interstitialcy is 0.01 t o 0.04 eV a t high temperatures, in AgBr t h e value is about 0.1 eV. In the G u r n e y - M o t t theory of latent image formations, it is supposed t h a t t h e grow- ing cluster quickly captures a photoelectron, a n d then the negative charge helps to attract a nearby silver ion. Y o u have n o t included this effect in your theory, it might help t o explain t h e appearance of very small migration energies.
J. F . GIULIANI. — O u r suggestion t h a t t h e colloid formation occurs primarly in a surface region is based on the fact t h a t o u r observed enthalpies of formation a n d migration both appear t o b e m u c h smaller than in bulk silver halide crystals. W e have n o t been able t o measure an enthalpy of migration, b u t only to place a n upper limit of a b o u t 0.01 eV.
M . W E N T Z . — Have you checked that y o u have real silver halide microcrystals within t h e glass matrix ? F o r we k n o w from Schott C o m p a n y (Mainz) that t h e particles in the glass matrix almost consist of glass enriched with A g+- i o n s a n d C l_- i o n s .
J. F . GUILIANI. — W e infer from several experi- mental methods that the particles of t h e separated phases contain in general three regions : a crystalline silver halide central core, a non-crystalline region having approximately the same composition as t h e core, a n d a glassy region similar in composition t o t h e matrix glass b u t depleted in metal ions. This is in complete agreement with the view of D r . Gliemeroth of Schott, a n d also with previous w o r k of Fanderlik. O u r data on the dynamics of silver colloid formation as a func- tion of temperature suggest t h a t the process we observe is occuring in the noncrystalline silver halide region.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1976791
