Line-Shape Definitions

Some common line-shape definitions used in CasaXPS are:

GL(p) = Gaussian/Lorentzian product formula where the mixing is determined by m = p/100, GL(100) is a pure Lorentzian while GL(0) is pure Gaussian[1].
SGL(p) = Gaussian/Lorentzian sum formula where the mixing is determined by m = p/100, SGL(100) is a pure Lorentzian while SGL(0) is pure Gaussian [1].

Note: The contribution of the spectrometer is Gaussian in shape while the natural core level line-shape is Lorentzian (with a small degree of tailing or asymmetry to higher binding energy). The K(alpha) X-ray source line-shape is also Lorentzian in shape [2].

A(a,b,n)GL(p) = Gaussian/Lorentzian product modified by an asymmetric form. Parameters a and b change the shape of the asymmetry while n defines the width of the Gaussian component used to convolute the shape of the profile [1].

LA(α, β, m) = Asymmetric line-shape where α and β define the spread of the tail on either side of the Lorentzian component. The parameter m specifies the width of the Gaussian used to convolute the Lorentzian curve. If values of α and β greater than unity are used this line-shape will correct a problem with previous asymmetric line-shapes (like A(a,b,n)GL(p) above) that tend to incorrectly estimate the peak area by incorporating area under the curve from binding energies well above the peak profile [3,4].

1) N. Fairley,, © Casa software Ltd. 2005
2) D. Briggs "Surface Analysis of Polymers by XPS and Static SIMS" Cambridge University Press, Cambridge (1998) 53.
3) M.C. Biesinger, B.P. Payne, L.W.M. Lau, A. Gerson, R.St.C. Smart, Surf. Interface Anal. 41 (2009) 324-332.
4) N. Fairley, personal communication.