Effect of ultraviolet irradiation on oxide fine grains studied with positron annihilation and ESR

被引：6

作者：

Saito, H ^{[1
]}

Hyodo, T ^{[1
]}

机构：

[1] Univ Tokyo, Grad Sch Arts & Sci, Inst Phys, Meguro Ku, Tokyo, Japan

来源：

POSITRON ANNIHILATION: ICPA-11 - PROCEEDINGS OF THE 11TH INTERNATIONAL CONFERENCE ON POSITRON ANNIHILATION, KANSAS CITY, MISSOURI, USA, MAY 1997 | 1997年 / 255-2卷

关键词：

positronium; ultraviolet irradiation; silica-aerogel; silica; alumina; ESR; spin conversion;

D O I：

10.4028/www.scientific.net/MSF.255-257.463

中图分类号：

T [工业技术];

学科分类号：

08 ;

摘要：

Effect of ultraviolet irradiation on oxide powders is examined with positron lifetime and ESR measurements. Silica-aerogel, silica powder and alumina powder are irradiated by a low-pressure mercury lamp at low temperatures. Remarkable changes in positron lifetime spectra are observed for silica-aerogel baked at 200 degrees C and the alumina powder showing spin-exchange reaction of positronium atoms with irradiation-induced paramagnetic centers on the grain surfaces, while no change induced by ultraviolet irradiation is observed in the silica-aerogel baked at 800 degrees C and the silica powder. ESR measurements show formation of -OCH2 radicals on the surfaces of silica-aerogel baked at 200 degrees C. Ortho-para conversion cross-section for the collision of positronium with a -OCH2 radical is estimated to be on the order of 10(-22)m(2).

引用

页码：463 / 465

页数：3

共 4 条

[1] THE EXISTENCE OF 3 O-PS STATES IN FINE POWDERS AT LOW-TEMPERATURES [J].

DAUWE, C ;

CONSOLATI, G .

JOURNAL DE PHYSIQUE IV, 1993, 3 (C4) :161-167

[2] ORTHOPOSITRONIUM STUDY OF POSITRON-IRRADIATION-INDUCED SURFACE-DEFECTS IN ALUMINA POWDER [J].

DAUWE, C ;

MBUNGUTSUMBU .

PHYSICAL REVIEW B, 1992, 45 (01) :9-19

[3]

SAITO H, 1995, PHYS REV B, V52, P689

[4] AN ELECTRON SPIN RESONANCE STUDY OF RELATIVE STABILITIES OF FREE RADICALS TRAPPED IN IRRADIATED METHANOL AT 77DEGREES K [J].

SULLIVAN, PJ ;

KOSKI, WS .

JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1963, 85 (04) :384-&

← 1 →