Demonstration of femtosecond broadband X-rays from laser wakefield acceleration as a source for pump-probe X-ray absorption studies af Behm, K, Hussein, AE, Zhao, TZ, Baggott, RA, Cole, JM, Hill, E, Krushelnick, K, Maksimchuk, A, Nees, J, Rose, SJ, Thomas, AGR, Watt, R, Wood, JC, Yanovsky, V, Mangles, SPD