Question 3: …
Question 3: (6) In general, an atomic resolution phase contrast image shows: The object exit surface wavefunction The projected crystal field potential The crystal field potential convolved with the contrast transfer function The object exit wavefunction convolved with the point spread function for weak phase approximation
Read DetailsQuestion 9: a) The contrast transfer function, H, can someti…
Question 9: a) The contrast transfer function, H, can sometimes be written as a product of two terms: H(u)=E(u)B(u) Within the weak phase object approximation, the B(u) term can be simplified to B(u)=exp(iχ(u))∼sin χ(u) and E(u) is referred to as the envelope function. Which lens is most closely associated with the contrast transfer function what lens parameters are the most important? (2) Discuss the factors that contribute to E(u). (2) b) You make measurements of the contrast transfer function of a TEM operating at 300 kV. The contrast transfer function measured at 3 different defocus values are shown below. The orange curve is the envelop function and the gray curve is the contrast transfer function. You are interested in studying a sample with important Miller plane spacings of 2.3 and 1.9Å. Explain the advantages and disadvantages of using each of the three imaging condition to investigate your sample. Which condition is best and why? (4) Estimate the spherical aberration coefficient. (2)
Read DetailsQuestion 8: …
Question 8: (6) Which of the following statements is true about extinction distance: It depends on the arrangement of atoms in a crystal or the miller indices It depends on the wavelength of the electron beam It depends on the density of the material It depends on the nature of the electron beam (incident or diffracted)
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