Line of sight techniques: Providing an inventory of all species arriving at and departing from a surface

被引:20
作者
Chan, ASY [1 ]
Skegg, MP [1 ]
Jones, RG [1 ]
机构
[1] Univ Nottingham, Sch Chem, Dept Phys Chem, Nottingham NG7 2RD, England
来源
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A-VACUUM SURFACES AND FILMS | 2001年 / 19卷 / 04期
关键词
D O I
10.1116/1.1349188
中图分类号
TB3 [工程材料学];
学科分类号
0805 ; 080502 ;
摘要
Line of sight (LOS) techniques comprise those methods in which species emanating from a surface (atoms, molecules. and radicals) undergo just a single pass through the ionization volume of a mass spectrometer before being pumped. This is achieved by enclosing the mass spectrometer within a cryoshield fitted with appropriate apertures, such that line of sight is established only between a patch on the sample surface (approximate to7 mm diameter) and the ionization volume. All LOS techniques are free from extraneous signals and have approximately equal detection probabilities for all species. Line of sight temperature programmed desorption, sticking probability (LOSSP), and product desorption (LOSPD) provide powerful and reliable ways of studying all aspects of surface kinetics, by allowing an inventory of all species arriving at and departing from a surface, for any combination of partial pressures, surface temperature, surface composition, and surface structure. Here we illustrate LOSSP and LOSPD using the reactions of 1-bromo-2-chloroethane, BrCH2CH2Cl,(BCE) and iodotrifluoromethane, CF3I, on Cu(111). For BCE we show that there is a 1:1 correspondence of product ethene to reactant BCE during dissociative adsorption at T > 253 K, and that the dissociative adsorption is nonactivated with a transition state 11 +/- 2.5 kJ mol(-1) below zero (0=molecule at infinity). For CF3I dissociative adsorption occurs at room temperature with a sticking probability of 0.96 +/-0.02 to produce CF2 which can either desorb as gaseous CF2 radicals (observed) or undergo a coupling reaction and then desorb as gaseous C2F4 (also observed). No other gas phase products were observed. (C) 2001 American Vacuum Society.
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页码:2007 / 2012
页数:6
相关论文
共 11 条
[1]   Surface dynamics using pulsed electron beams [J].
Chan, ASY ;
Jones, RG .
SURFACE SCIENCE, 2000, 451 (1-3) :232-237
[2]   Electron-stimulated chemistry of CF3I adsorbed on Ag(111) C-F bond cleavage and C-C coupling [J].
Fieberg, JE ;
Szabo, A ;
White, JM .
JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS, 1996, 92 (23) :4739-4748
[3]   Selective and facile C-F bond activation of trifluoromethyl groups on Cu(111) [J].
Hou, YC ;
Chiang, CM .
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 1999, 121 (35) :8116-8117
[4]   Surface kinetics using line of sight techniques: the reaction of chloroform with Cu(111) [J].
Jones, RG ;
Clifford, CA .
PHYSICAL CHEMISTRY CHEMICAL PHYSICS, 1999, 1 (22) :5223-5228
[5]   Reaction and sticking probabilities using line of sight techniques: iodine on Al(111) [J].
Jones, RG ;
Fisher, CJ .
SURFACE SCIENCE, 1999, 424 (01) :127-138
[6]   MERCURY ADSORPTION ON NI(111) .1. ADSORPTION AT ROOM-TEMPERATURE AND ABOVE [J].
SINGH, NK ;
JONES, RG .
SURFACE SCIENCE, 1990, 232 (03) :229-242
[7]  
SKEGG MP, UNPUB
[8]  
STEIN SE, 2000, NIST CHEM WEBBOOK NI
[9]   Thermal chemistry of CF3I on Ag(111): A TPD and RAIRS study [J].
Szabo, A ;
Converse, SE ;
Whaley, SR ;
White, JM .
SURFACE SCIENCE, 1996, 364 (03) :345-366
[10]   Molecular and dissociative adsorption of 1-bromo-2-chloroethane on Cu(111) [J].
Turton, S ;
Kadodwala, M ;
Jones, RG .
SURFACE SCIENCE, 1999, 442 (03) :517-530