K to L shell vacancy transfer probabilities (eta kappa(L)) for 26 elements in the atomic region 23 <= Z <= 57 were determined by measuring the I-K beta/I-k alpha intensity ratios. The targets were irradiated with gamma-photons at 59.543 keV from Am-241 annular source. The K X-rays from different targets were detected with a high resolution Si(Li) detector. Theoretical values were calculated using the radiative acid radiationless transition rates of these elements. The measured values of eta(KL), are compared with the theoretical values and data of others. The measurement vacancy transfer probabilities are least-square fitted to third-order polynomials to obtain analytical relations that represent these probabilities as a function of atomic number. The measured values of eta(KL) for V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se and Br are being reported here for the first tune.