Fig. 41: Spin-resolved circularly polarised 2p3/2 (L3) resonant valence band photoemission spectrum of CuO. The thick solid line in the top panel is the sum of two spectra, one taken with parallel and the other with antiparallel alignment of the photon spin and electron spin. The thin line with open circles is the spin polarisation, calculated as the ratio between the difference and sum spectrum. The zero check measurement verifies a correct experimental set-up [1].