Optical transitions ofRh2+in NaCl crystals studied by electron spin resonance and magnetic circular dichroism

Abstract

Electron spin resonance, magnetic circular dichroism, and optical absorption spectra of a paramagnetic Rh 2ϩ complex are investigated in Rh 3ϩ doped solution-grown NaCl single crystals. x irradiation of the crystals at 77 K followed by a warm-up to room temperature results in the formation of a stable low-spin Jahn-Teller distorted RhCl 6 4Ϫ complex possessing D 4h symmetry. The unpaired electron is largely localized in the 4d z 2 orbital of the Rh 2ϩ (4d 7 ) which is involved in a type molecular bond with two symmetrically placed Cl Ϫ ions along ͗001͘. The magnetic circular dichroism and optical absorption measurements at 1.4 K reveal two main bands around 12 200 cm Ϫ1 and 16 200 cm Ϫ1 . Within the octahedral Tanabe-Sugano formalism of the Rh 2ϩ these two absorptions are associated with two vibronically allowed 2 E g → 2 T 1g , 2 T 2g molecular transitions. This assignment is in quantitative agreement with the analysis of the g matrix components. A small MCD feature at 15 200 cm Ϫ1 is tentatively associated with two coinciding 2 E g → 2 T 1g , 2 T 2g transitions of another, probably a ligand-exchanged, Rh 2ϩ center.

Origin of warping in theE⊗eJahn-Teller problem: Quadratic vibronic coupling versus anharmonicity and application toNaCl:Rh2+García‐Fernández1, Берсукер2, Aramburu3 et al. 2005Phys. Rev. B754711View full textAdd to dashboardCite

“…The resulting geometries at the minima of the APES are fully compatible with those previously obtained for these systems and with the experimental data. [23][24][25][26][27][32][33][34][35][36][37] Newly obtained CASPT2 geometries of NaCl: Rh 2+ are very similar to those obtained earlier by DFT method with the distinction that the value of e frequencies, JT energies, and the barrier ␦ obtained using CASPT2 are somewhat larger. This is because LDA-GGA methods usually overestimate the electronic correlation energy.…”

“…Specific calculations using ab initio multireference and Density Functional Theory ͑DFT͒ methods were performed on systems of different nature: NaCl: Rh 2+ and triangular molecules Ag 3 , Cu 3 , K 3 , and Na 3 . The NaCl: Rh 2+ system has been chosen because of the available experimental data [23][24][25] and previous partial calculations. [26][27][28] Low temperature electron paramagnetic resonance ͑EPR͒ and electron nuclear double resonance ͑ENDOR͒ data [23][24][25] reveal the presence of JT distortions resulting in the elongated RhCl 6 4− complex ͑Fig.…”

Jahn‐Teller distortions and off centre motions in impurities: Microscopic insight

“…This fact is thus in agreement with reported EPR data [9]. It is also worth noting that the minimum for the (3z 2 -r 2 ) 1 state is found at u 0 = 0.0875 Å while that for (x 2 -y 2 ) 1 is obtained at u 0 = -0.0625 Å.…”

Coherent tunneling inCu2+- andAg2+-doped MgO andGarcía‐Fernández1, Sousa2, Aramburu3 et al. 2005Phys. Rev. B272250View full textAdd to dashboardCite

“…For comparison, computed values are also given for NaCl: Rh 2+ displaying a static JT effect. 25 For the same reason, Table I also includes the DFT values of R oct , 0 , E JT , and e , although the poor self-consistent field convergence in the computed E ± ͑ , ͒ curves are prevented in a few cases to obtain reliable values for the parameters collected in Tables I and II. CASPT2 and DFT values of R oct and 0 given in 14 can be ascribed to the neglect of the contribution of the symmetric a 1g mode to the ⌬E Ϸ 1100 cm −1 separation between the electric dipole origin and the maximum of the associated broad band. For transition-metal impurities at octahedral sites ⌬E Ϸ S a a + S e e , 27 where E JT ϵ S e e and S e ͑S a ͒ is the Huang-Rhys factor of the e g ͑a 1g ͒ mode.…”