 Solution

ID: past-exam-of-the-chemistry-course-of-the-year-4-of-the-natural-sciences-course-of-the-university-of-cambridge/2022/paper-3/section-b/38/a/solution

The binding energies are referred to the common Fermi level. Immediately outside the copper surface, conservation of energy gives

K_{s} = h ν - E_{B} - ϕ_{s} = 515.0 - 399.2 - 4.0 = 111.8 eV .

This is the emitted photoelectron energy at the sample. On reaching the electrically connected, unbiased analyser, its energy is instead

K_{a} = h ν - E_{B} - ϕ_{a} = 111.4 eV

. The 0.4 eV difference is the contact-potential correction, not an additional binding-energy shift. Distinguishing these two reference positions is essential for the retarding-voltage calculation.

 New to topics? Read the docs here!