Structure and wavelength of the Cu K2 x-ray emission line

The Cu K emission spectrum was measured with a novel channeled monolithic double-crystal spectrometer. The wavelength of the Cu K2 line was determined to be (Cu K2)=1.544 425 6 A (1.2 ppm). A small shoulder was detected on the low-energy side of the K2 peak at a shift of 2.2 eV. To an accuracy lower than 1%, no other structure was detected. The width and asymmetry parameters obtained for the K2 peak are in good agreement with previous measurements. The K2 line shape is analyzed within the framework of the radiative-Auger and many-body-excitation theories of x-ray emission. A well-defined lifetime width of the K2 line is obtained, yielding a K-level width of 1.560.04 eV, in excellent agreement with theoretical and semiempirical predictions. The applicability of the radiative-Auger, multivacancy, and many-body theories to the measured data is discussed.