Multielectron X-ray photoexcitation measurements in krypton

X-ray photoabsorption measurements were carried out on krypton near the 1s ionization threshold, by use of synchrotron radiation. A rich, well resolved spectrum of simultaneous two- and three-electron excitations is detected. Feature identification is supported by both relativistic and nonrelativistic calculations. The data support in detail the Z+1 approximation for both two- and three-electron excitations. No indication of a preferred Coster-Kronig decay channel for 1s4s hole states is found, in contrast with argon. The partial cross sections are in good accord with shakeup theory and photoelectron data on other noble gases.