Photochemistry in CH3I adlayers on TiO2(110) studied with postirradiation thermal desorption

被引:19
作者
Kim, SH [1 ]
Stair, PC [1 ]
Weitz, E [1 ]
机构
[1] Northwestern Univ, Dept Chem, Evanston, IL 60208 USA
关键词
D O I
10.1021/la980218n
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
The reaction dynamics of photofragments produced by UV photolysis of neat CH3I films, adsorbed on defect-free TiO2(110), have been investigated using postirradiation temperature programmed desorption (PITPD). At low fluences, the film structure remains frozen, retaining photofragments and reaction products in the film. CH4, C2H6, I-2, CH2I2, and C2H5I are detected in PITPD. CH4 is a product of translationally hot methyl radicals reacting with CH3I. Desorption of the CH4 trapped in the CH3I films is limited by diffusion in the films. The I-containing products detected in PITPD come predominantly from reactions of trapped I, CH2I, and CH3 radicals, which occur during the TPD process. The desorption of I-containing products in PITPD follows desorption-limited kinetics on the TiO2(110) surface. Far C2H6 detected in PITPD, it is not clear whether the dominant reaction pathway involves hot or cold radicals. Electrons produced in the TiO2 substrate upon UV irradiation do not induce significant dissociation of CH3I adsorbed on the (110) surface and thus do not contribute significantly to fragment reactions.
引用
收藏
页码:4156 / 4161
页数:6
相关论文
共 50 条
[1]  
BRUNS JC, 1990, THESIS NW U
[2]   TEMPORARY NEGATIVE-IONS IN THE CHLOROMETHANES CHCL2F AND CCL2F2 - CHARACTERIZATION OF THE SIGMA-STAR ORBITALS [J].
BURROW, PD ;
MODELLI, A ;
CHIU, NS ;
JORDAN, KD .
JOURNAL OF CHEMICAL PHYSICS, 1982, 77 (05) :2699-2701
[3]   Layer-by-layer removal of GaAs(110) by bromine [J].
Cha, CY ;
Weaver, JH .
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B, 1996, 14 (06) :3559-3562
[4]   PHOTOPRODUCT CHARACTERIZATION AND DYNAMICS IN THE 248 NM PHOTOLYSIS OF CH3I THIN-FILMS ON AG(111) [J].
COON, SR ;
MYLI, KB ;
GRASSIAN, VH .
JOURNAL OF PHYSICAL CHEMISTRY, 1995, 99 (44) :16416-16424
[5]   CONSTRUCTION OF A KINETIC-MODEL FOR THE IODINE CH3I PHOTO-DISSOCIATION LASER - CALCULATION OF CROSS-SECTIONS AND COMPARISON WITH EXPERIMENT [J].
COSTELA, A ;
FIGUERA, JM ;
MARTIN, M ;
PEREZ, JM ;
VALLE, L .
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS I, 1980, 76 :30-42
[6]   DIRECT EVIDENCE FOR CHARGE-TRANSFER PHOTODISSOCIATION AT A METAL-SURFACE - CCL4/AG(111) [J].
DIXONWARREN, SJ ;
JENSEN, ET ;
POLANYI, JC .
PHYSICAL REVIEW LETTERS, 1991, 67 (17) :2395-2398
[7]   ELECTRONIC EXCITATIONS AT OXYGEN DEFICIENT TIO2(110) SURFACES - A STUDY BY EELS [J].
ERIKSEN, S ;
EGDELL, RG .
SURFACE SCIENCE, 1987, 180 (01) :263-278
[8]   THE ROLE OF ADSORBATE STRUCTURE IN THE PHOTODISSOCIATION DYNAMICS OF ADSORBED SPECIES - METHYL-IODIDE MGO(100) [J].
FAIRBROTHER, DH ;
BRIGGMAN, KA ;
STAIR, PC ;
WEITZ, E .
JOURNAL OF CHEMICAL PHYSICS, 1995, 102 (18) :7267-7276
[9]   KINETIC STUDY OF REACTION CHI3+HI-]]-CH2I2+I2 . A SUMMARY OF THERMOCHEMICAL PROPERTIES OF HALOMETHANES AND HALOMETHYL RADICALS [J].
FURUYAMA, S ;
GOLDEN, DM ;
BENSON, SW .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1969, 91 (27) :7564-&
[10]  
Furuyama S, 1969, INT J CHEM KINET, V1, P283