Crystal field analysis of the ground and excited state absorption of a Cr4+ ion in LiAlO2 and LiGaO2 crystals

Abstract

The exchange charge model of crystal field theory has been used to analyze the ground and excited state absorption of tetrahedrally coordinated Cr 4+ ion in lithium aluminum oxide LiAlO 2 (γ-phase) and lithium dioxogallate LiGaO 2 . The parameters of the crystal field acting on the Cr 4+ ion are calculated from the crystal structure data, taking into account the crystal lattice ions located at distances up to 12.744Å in LiGaO 2 and 13.180Å in LiAlO 2 . The obtained energy level schemes were compared with experimental ground and excited state absorption spectra and literature data on the application of other crystal field models (the angular overlap model and Racah theory) to the considered crystals; a good agreement with experimental data is demonstrated.

Spin-flip luminescence

“…1d and 5b). Hence spinflip emission from a 1 E → 3 A 2 transition could be achieved with a high ligand field splitting in tetrahedral d 2 complexes [147]. In fact, tetrahedral Cr IV complexes with anionic alkyl or aryl ligands Cr17-Cr22 emit between 897 and 1025 nm at 4 K and were proposed as optically addressable qubit candidates (Scheme 2, Table 2) [130,131].…”

“…1b) [160]. The emission bands of the known Mo III complexes Mo1 3-, [Mo III (NCS) 6 ] 3-Mo2 3-, mer-Mo III Cl 3 (L) 3 Mo3-Mo5 (L = py, urea, tu; py = pyridine, tu = thiourea), mer-Mo III Br 3 (urea) 3 Mo6, fac-Mo III (Me 3 [9]aneN 3 )X 3 2) [128,130,147] Mo7-Mo9 (Me 3 [9]aneN 3 = 1,4,7-trimethyl-1,4,7-triazacyclononane; X = Cl, Br, I) and fac-[Mo III {HB(Me 2 Pz) 3 } Cl 3 ] -Mo10 -({HB(Me 2 Pz) 3 } -= tris(3,5-dimethyl-1H-pyrazol-1-yl)hydroborate) appear between 1090 and 1400 nm with emission lifetimes of several hundred nanoseconds and poor quantum yields of 0.0061-0.012% (Scheme 3, Table 3) [160,161]. Multiphonon relaxation via C-H oscillators of the ligands or solvent molecules might play an important role in the deactivation of the excited states.…”

“…Fig. 5 Schematic energy-level ordering and exemplary microstates in a trigonal-bipyramidal V III complex V4 and b tetrahedral Cr IV complexes Cr17-Cr22 (Scheme 2, Table2)[128,130,147] …”