Resonant inelastic X-ray scattering as a probe of J eff = 1/2 state in 3d transition-metal oxide oleh H. Y. Huang, A. Singh, C. I. Wu, J. D. Xie, J. Okamoto, A. A. Belik, E. Kurmaev, A. Fujimori, C. T. Chen, S. V. Streltsov, D. J. Huang