Mössbauer Effect in Surface Studies:Fe57on W and on Ag

The Mössbauer effect at crystal surfaces is discussed. ${\mathrm{Fe}}^{57}$ on the surface of W and Ag has been measured under ultrahigh vacuum. The W experiment yielded Debye temperatures of 406±12, 354±30, and 255±30°K in the bulk, along the surface normal, and parallel to the surface, respectively. In Ag the bulk Debye temperature was 253±12°K while the surface value was 380±30°K and showed no angular dependence. Quadrupole splitting in both experiments indicated surface field gradients of about -3×${10}^{16}$ V/${\mathrm{cm}}^2$.