Spectroscopy of structurally disordered hydrated iron fluoridotitanate in the regions of vibrational and electronic excitations

Yu V Gerasimova; A S Aleksandrovsky; N M Laptash; M A Gerasimov; A S Krylov; A N Vtyurin; A A Dubrovskiy

doi:10.1016/j.saa.2021.120244

Spectroscopy of structurally disordered hydrated iron fluoridotitanate in the regions of vibrational and electronic excitations

Spectrochim Acta A Mol Biomol Spectrosc. 2022 Jan 5:264:120244. doi: 10.1016/j.saa.2021.120244. Epub 2021 Jul 31.

Authors

Yu V Gerasimova¹, A S Aleksandrovsky², N M Laptash³, M A Gerasimov⁴, A S Krylov⁴, A N Vtyurin², A A Dubrovskiy⁴

Affiliations

¹ Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk, Russia; Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660079 Krasnoyarsk, Russia. Electronic address: jul@iph.krasn.ru.
² Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk, Russia; Institute of Engineering Physics and Radio Electronics, Siberian Federal University, 660079 Krasnoyarsk, Russia.
³ Institute of Chemistry, Far Eastern Branch of RAS, 690022 Vladivostok, Russia.
⁴ Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk, Russia.

PMID: 34365133
DOI: 10.1016/j.saa.2021.120244

Abstract

Raman and optical absorption spectra of disordered hydrated iron fluoridotitanate (HITF) single crystal were studied. Temperature transformations of the Raman spectra indicate independent ordering processes of the [TiF₆]^2- and [Fe(H₂O)₆]²⁺ complexes below the structural phase transition. The absorption spectrum in the near-infrared and visible ranges includes transitions from the high spin ground state ⁵T₂ of Fe²⁺ ion to the excited ⁵E state and a set of excited triplets. Analysis by Tanabe-Sugano method gives crystal field Dq = 490 cm^-1 and Racah parameters B = 340 cm^-1 and C = 1904 cm^-1. Considerable decrease of B parameter as compared to the free ion value indicates a decrease of interelectron repulsion in the disordered neighborhood of Fe²⁺ ions.

Keywords: Dynamics; Electronic excitations; Hydrated iron fluoridotitanate; Order-disorder; Phase transition; Raman.