On the Mn4+ R-line emission intensity and its tunability in solids

Mn4+-Doped Fluoride Nanocrystals Enable High-Resolution Red-Emitting X-ray Imaging Screens

“…The excitation bands in the UV and blue regions originate from the spin-allowed but parity-forbidden 4 A 2g → 4 T 1g and 4 A 2g → 4 T 2g transitions in Mn 4+ , respectively. , A series of narrow-band emissions between 610 and 650 nm, with the most intense peak centered near 630 nm, derives from the spin- and parity-forbidden 2 E g → 4 A 2g transitions in Mn 4+ (Figure a, b) . This series of emission peaks is attributed to the anti-Stokes ν 3 (t 1u ), ν 4 (t 1u ), ν 6 (t 2u ), and zero phonon line (ZPL) vibronic modes and the Stokes ν 6 (t 2u ), ν 4 (t 1u ), and ν 3 (t 1u ) vibronic modes, respectively. , Some shifts in the emission peaks can be observed between different compositions, which is related to the different crystal field strengths of Mn 4+ -doped ions, caused by differences in M–F bond strength between different compositions ,, (a dotted line is provided for guidance in Figure a). Additionally, the ZPL of K 3 AlF 6 :Mn 4+ NCs is stronger than that of other compositions, which has been previously observed in nonequivalent doped fluoride phosphors. − In fact, the intensity of the ZPL is mainly determined by the local symmetry of the Mn 4+ environment, and an increase in the ZPL line is associated with a reduction in local symmetry upon nonequivalent doping. ,, Figure c shows the photoluminescence decay curves at 630 nm emission upon excitation at 465 nm for NC colloidal solutions of different matrix compositions and a Mn 4+ concentration of about 2 at.…”

“…14 This series of emission peaks is attributed to the anti-Stokes ν 3 (t 1u ), ν 4 (t 1u ), ν 6 (t 2u ), and zero phonon line (ZPL) vibronic modes and the Stokes ν 6 (t 2u ), ν 4 (t 1u ), and ν 3 (t 1u ) vibronic modes, respectively. 14,18 Some shifts in the emission peaks can be observed between different compositions, which is related to the different crystal field strengths of Mn 4+ -doped ions, caused by differences in M−F bond strength between different compositions 4,22,25 (a dotted line is provided for guidance in Figure 2a). Additionally, the ZPL of K 3 AlF 6 :Mn 4+ NCs is stronger than that of other compositions, which has been previously observed in nonequivalent doped fluoride phosphors.…”

Enhancing the luminescence performance of an LED-pumped Mn4+-activated highly efficient double perovskite phosphor with A-site defectsvialocal lattice tuning

“…However, the ZPL of Mn 4+ ions in strictly symmetric octahedra is commonly hard to distinguish, which is caused by the weak intensity of the magnetic dipole transitions. 21 In this matrix, the inversion symmetry of the Ta 5+ ion sites occupied by Mn 4+ ions is significantly reduced due to the random occupation of the nearest cation A-site, meaning that the Laporte selection rule is broken by the lack of inversion centers of [MnO 6 ] octahedra and the ZPL of the Mn 4+ ions produces electric dipole transitions with greater intensities. On the other hand, the stronger local distortion in the doped Mn 4+ ion matrix facilitates the higher ZPL intensity.…”

“…4(d)). 21 In general, the E( 2 E g ) value of Mn 4+ ions is determined by the Racah parameters B and C, which are due to the nephelauxetic effect of different matrices. Thus, the nephelauxetic ratio β 1 reported by Brik et al was investigated to predict the emission wavelength of the LMTO phosphors doped with Mn 4+ ions based on the following equation: 37…”

“…20 That is, the vibronic sidebands have electric dipole character, while the ZPL with all-even parity nature exhibits that the electric dipole transitions are forbidden and the magnetic dipole transitions are allowed in a strictly symmetric octahedron. 21 In general, the intensity of the ZPL is much lower than the Stokes peak due to the weak magnetic dipole transition, which affects to some extent the emission intensity of the Mn 4+ ion-doped phosphor. 22 Importantly, the emission intensity of ZPL is determined only by the lattice structure where the Mn 4+ ions are located as there is no phonon participation.…”