McCoustra Essentials

Question 1

types of reactions on surfaces

Answer 1

Eeley-Rideal, Langmuir Hinshelwood and Kaesmo-Harris

Question 2

Eeley-Rideal reactions on surfaces

Answer 2

one reactants adsorbs, second reactants collides with adsorbed species, react to give product which desorbs

Question 3

Langmuir-Hinshelwood reactions on surfaces

Answer 3

two reactants adsorb, diffuse across surface and react to give product which desorbs

Question 4

Kaesmo-Harris reactions on surfaces

Answer 4

2 reactants adsorb, one species reacts with light and forms hot atom, hot atom is above any energy barriers to diffusion but remains bound to surface, rapidly diffuses across surface, reacts with other reactant forming product and product desorbs leaving fragment behind

Question 5

X-ray photoelectron spectroscopy

Answer 5

e- excited upon adsorption of x-ray photon, gives information on composition and chemical state by measuring core level e-

Question 6

auger emission spectroscopy

Answer 6

one e- goes down to fill core hole and another is emitted, highly surface sensitive, good for v. thin level adsorbates, gives little information on chemical state and high energy e- used may cause desorption

Question 7

temperature programmed desorption

Answer 7

measures rate of evolution of material from surface as it’s heated

Question 8

temperature programmed desorption experimentally

Answer 8

substrate and adsorbate in UHV, heated at uniform rate, detect change in pressure of desorbed species using QMS

Question 9

isothermal desorption

Answer 9

temp = constant, measures concentration of surface species as function of time using QMS