This picture is however oversimplified as the V d elec- trons are strongly correlated and the spectra are still largely influenced by the 1 s core hole potential. Keeping that in mind, we have simulated the pre-edge by combin- ing CI with LDA+DMFT calculations for which the one Our CI calculations confirm that for the ground state the occupancy ratio between the ( e π $_{g}$, a$_{1}$$_{g}$ ) and ( e π $_{g}$, e π $_{g}$) states is smaller in the PI than in the PM phase [8, 16]: The isotropic CI-based calculated XAS spectra in the pre-edge region reported in Fig. 1(c) agree well with the experimental data for both the energy splitting of fea- tures A and B and the ratio of their spectral weight (SW) which increases in the PM phase. particle part (LDA) input corresponds to the level dia- gram in Fig. 1(d). We concentrate our analysis to peaks A and B, since peak C relates mainly to the unoccupied e σ g orbitals. These hybridize much stronger with the oxy- gen ligands and thus lack direct information on the Mott transition; peak C may also be related to non-local exci- tations (not included here) [22] which sensitively depend on the metal-ligand distance. Let us also note that the V sites in V$_{2}$O$_{3}$ are non centrosymmetric which leads to an on-site mixing of V-3 d and V-4 p -orbitals and interference between dipole and quadrupole transitions [7] which has been included in our scheme. FIG. 1: (Color online) (a) V K -edge x-ray absorption spec- tra in (V 1$_{−}$ x Cr x ) 2 O 3 , x = 0 . 011 powder sample measured as a function of temperature (T) in the PM (200 K, solid line) and PI (300 K, dotted line) phases by PFY XAS; below, PM − PI spectral difference; (inset) pre-edge region. (c) Cal- culated isotropic CI V K -edge PM and PI spectra of V 2 O 3 . The spectra are compared to the T-dependent experimental data shown in the same energy window (b). (d) From LDA (starting point for our LDA+DMFT and CI calculations) we obtain that the cubic part of the ligand field splits the V d- levels in t$_{2}$$_{g}$ and e$_{g}$ by 10 Dq ∼ 2 eV, and that the small trigonal distortion further separates the t$_{2}$$_{g}$ into a$_{1}$$_{g}$ and e π g by Δ trig ∼ 0.3 eV. 5470 5465 GLYPH<s65> GLYPH<s66> GLYPH<s67> 5520 5500 5480 5460  PM  PI GLYPH<s40>GLYPH<s97>GLYPH<s41> (PM-PI) x 4 5469 5465 GLYPH<s40>GLYPH<s99>GLYPH<s41> GLYPH<s67>GLYPH<s65>GLYPH<s76>GLYPH<s67>GLYPH<s46> GLYPH<s65> GLYPH<s66> 5469 5465 GLYPH<s40>GLYPH<s98>GLYPH<s41> GLYPH<s69>GLYPH<s88>GLYPH<s80>GLYPH<s46> (T) GLYPH<s65> GLYPH<s66> Photon Energy (eV) Intensity (arb. units) Intensity (arb. units) cubic field trigonal field GLYPH<s40>GLYPH<s100>GLYPH<s41> high quality samples of (V$_{1}$$_{−}$$_{x}$Cr$_{x}$)$_{2}$O$_{3}$ with various dop- ing in the PM ( x = 0) and PI phases ( x = 0 . 011, and 0.028) at ambient conditions. The MIT was also crossed for the 0.011 doping by changing temperature and for the 0.028 doping by pressure. To obtain the best reso- lution, the XAS spectra were acquired in the so-called partial fluorescence yield (PFY) mode [18], monitoring the intensity of the V-K α (2 p → 1 s ) line as the incident energy is swept across the absorption edge. Compared to standard XAS, the PFY mode provides better resolved absorption spectra as these are partly free from core-hole lifetime broadening effect. The gain is particularly ap- preciable at the transition metal K pre-edges as the 1 s core-hole is extremely short lived with respect to the 2 p core-hole and the dipolar tail is strongly reduced. The V-K α line was measured with the help of a IXS spec- trometer equipped with a Ge(331) spherically bent ana- lyzer. For the temperature dependence, the crystals were mounted in a cryostat installed on the spectrometer. On the other hand, measuring the PFY mode turned out to be difficult under pressure because of the weak fluores- cence signal in the pressure cell and we opted for standard XAS measurements in transmission mode. To maximize the throughput, a powder sample ( x = 0 . 028) was loaded in a diamond anvil cell equipped with composite anvils made of a perforated diamond capped with a 500- µm thin diamond anvil. Pressure was measured in-situ by standard ruby fluorescence technique. We used silicon oil as a pressure transmitting medium. The T-dependent absorption spectra are displayed in Fig. 1(a) for both PM (200 K) and PI (300 K) phases for the x = 0 . 011, powder sample. The spectra have been normalized to an edge jump of unity. We will focus on the pre-edge region, where information about the V d - states can be easier extracted. It can be decomposed into three spectral features (A,B,C) which all vary in intensity as the system is driven through the MIT whereas only C is considerably broadened (Fig. 1(a), inset). Notice that no feature is observed below peak A contrary to the early results of Ref. [19] but in agreement with the more recent data of Ref. [20]. Within a simplified atomic like picture, one could directly relate the intensity of features A,B and C to the unoccupied states. Starting from a V- t 2 2 $_{g}$, S = 1 configuration, one can either add an electron to the t$_{2}$$_{g}$ subshell (split into one a$_{1}$$_{g}$ and two e π g states under trigonal distortion of the V sites [21] as shown in Fig. 1(d)) yielding peaks A and B, or add an electron to the e σ g sub-shell which gives rise to the broader peak C. In this picture, one could associate peak A with a spin quartet ( S = 3 / 2) and peak B with a spin doublet ( S = 1 / 2), split by the Hund’s rule exchange. 2