Optical properties of Ga2Se3 and Ga2Se3:Co2+ single crystals

Study on the Absorption Spectra of Ga2Se3:Co2+ Single Crystals

“…But there are some differences between the reassigned results and the results [5] mentioned in (i) Yoon et al drew the conclusion that the 4 T 1 ( 4 P) state of the Co 2+ ion sited in a T d symmetry split into four sublevels Γ 6 (14865 cm −1 ), Γ 8 (13926 cm −1 ), Γ 7 (13465 cm −1 ), and Γ 8 (12937 cm −1 ) due to the first-and second-order spin-orbit coupling effects [5]. In our opinion, the assignment of Γ 6 (14865 cm −1 ) was wrong.…”

“…The Racah parameters in a free Co 2+ ion are [6] In the experiment, the transition value from the ground state 4 T 2 ( 4 F) to the excited state 4 T 2 ( 4 F) was 3451 cm −1 [5]. The crystal field parameter D q calculated from (2) - (3) amounts to 345 cm −1 .…”

“…But in [5], different values of crystal field parameter D q , such as 345 cm −1 , 349 cm −1 , and 642 cm −1 , respectively, were used to assign the transitions 4 A 2 ( 4 F) → 4 T 2 ( 4 F), 4 A 2 ( 4 F) → 4 T 1 ( 4 F), and 4 A 2 ( 4 F) → 4 T 1 ( 4 P). In theory that method is not in accordance with the physical meanings of crystal field parameter D q .…”

“…(ii) The first-and second-order perturbation were adopted to calculate and assign the sublevels in [5]. But using this method there were some errors in the assigned results.…”

“…Using the chemical transport reaction method Yoon et al obtained Ga 2 Se 3 and Ga 2 Se 3 :Co 2+ single crystals and measured their optical absorption spectra to reveal the impurity optical absorption mechanism of the Co 2+ ion [5]. They assigned those absorption peaks according to the crystal field theory but there were some errors in the assigned results.…”