Quantitative information from electron spectroscopy for chemical analysis requires the use of suitable atomic sensitivity factors. An empirical set has been developed, based upon data from 135 compounds of 62 elements. Data upon which the factors are based are intensity ratios of spectral lines with F l s as a primary standard, value unity, and K2p3/2 as a secondary standard. The data were obtained on two instruments, the Physical Electronics 550 and the Varian IEE-15, two instruments that use electron retardation for scanning, with constant pass energy. The agreement in data from the two instruments on the same compounds is good. How closely the data can apply to instruments with input lens systems is not known. Calculated cross-section data plotted against binding energy on a log-log plot provide curves composed of simple linear segments for the strong lines: Is, 2~,~, 3d5/2 and 4f712. Similarly, the plots for the secondary lines, 2s, 313312, 4dSl2 and 5dSl2, are shown to be composed of linear segments. Theoretical sensitivity factors relative to F l s should fall on similar curves, with minor correction for the combined energy dependence of instrumental transmission and mean free path. Experimental intensity ratios relative to F l s were plotted similarly, and best fit curves were calculated using the shapes of the theoretical curves as a guide. The intercepts of these best fit curves with appropriate binding energies provide sensitivity factors for the strong lines and the secondary lines for all of the elements except the rare earths and the first series of transition metals. For these elements the sensitivity factors are lower than expected, and variable, because of multi-electron processes that vary with chemical state. From the data it can be shown that many of the commonly-accepted calculated cross-section data must be significantly in error-as much as 40% in some cases for the strong lines, and far more than that for some of the secondary lines. I N T R O D U C T I O NOf the techniques useful for analyzing the first few atomic layers of surfaces, ESCA (electron spectroscopy for chemical analysis), known also as XPS (X-ray photoelectron spectroscopy) is the most useful for quantitative analysis. If we assume a solid that is homogeneous to a depth of 10-20 nm (several electron mean free paths), the number of photoelectrons detected per second from an orbital of constituent atoms is given by(1) where n is the number of atoms per cm3 of the element of interest, f is the flux of X-ray photons impinging on the sample, in photons cmp2 spl, (T is the photoelectric cross-section for the particular transition in cm2 per atom, 4 is the angular efficiency factor for the instrumental arrangement (angle between photon path and emitted photoelectron that is detected), y is the efficiency of production in the photoelectric process to give photoelectrons of normal energy (with final ionic state the ground state), A is the area of the sample from t Author to whom correspondence should be addressed. which photoelectrons c...

Experiments providing multi‐point data on electron mean free paths vs. energy in pure materials have been reviewed for energies from 150 to 4000 eV. With the assumption that the simple equation λ=kEm can approximate the data, one obtains values of m between 0.53 and 0.80. Observations by ESCA of widely spaced photoelectron lines for Mg, Cu, Zn, Ga, Ge and As also lead to the conclusion that the exponent is considerably larger than 0.5, and is more likely in the range 0.65‐0.75.

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