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Rare-Earth Ions and Fiber Laser Fundamentals
Published in Johan Meyer, Justice Sompo, Suné von Solms, Fiber Lasers, 2022
Johan Meyer, Justice Sompo, Sune von Solms
Long before the demonstration of the first working laser, rare-earth materials were a subject of intense research interest because of their optical properties. In fact, observation showed that rare-earths materials exhibited sharp intense spectral lines suggesting that radiative transitions were taking place within the 4f electronic shell, contradicting Laporte selection rules. In 1937 J.H van Vleck published an article (Vleck 1937) in which he reported this “bizarre” phenomenon which he referred to as “The puzzle of the Rare-earth spectra in solids”. In these conditions, to explain the relatively strong intensity and spectral features of spectra lines observed, it was suggested that this “puzzle” originated from four possibilities, namely, 4f to 5d transitions, electric dipole transition, magnetic dipole transition, or electric quadrupole transition. A transition from 4f to 5d would result in broad spectral line contrary to the sharp lines observed, therefore this possibility was eliminated. Magnetic transition on the other hand account only for a few numbers of transition and cannot be retained as responsible for the observed spectra. Quadrupole radiation account for all transitions but their rather weak strengths do not justify the relatively high intensities observed. The only possibility left is electric dipole transition which is in principle forbidden by Laporte selection rules as it was reported earlier. Van Vleck in 1937 predicted that the crystal host was responsible for the “puzzle”(Vleck 1937). The prediction was later confirmed by Broer et al. in 1945 (Broer et al. 1945).
Borate Phosphor
Published in S. K. Omanwar, R. P. Sonekar, N. S. Bajaj, Borate Phosphors, 2022
Eu3+ ion is another important rare earth ion and often emits red light corresponding to the transitions 5D0 → 7FJ (J = 1–6). According to the Judd–Ofelt theory [190,191], the intensity of the magnetic dipole transition (5D0 → 7F1) does not depend upon the local environment, whereas the electric dipole transition (5D0 → 7F2) is very sensitive to the symmetry of the cation surroundings. When the Eu3+ ions act as an activator, occupy sites with noninversion symmetry, 5D0 → 7F2 transitions will be dominant, but if the Eu3+ ions occupy sites with inversion symmetry, the emission corresponding to 5D0 → 7F21 is prominent.
Photoluminescence Mechanism and Key Factors to Improve Intensity of Lanthanide Doped Tungstate/Molybdate Phosphors with Their Applications
Published in Vikas Dubey, Sudipta Som, Vijay Kumar, Luminescent Materials in Display and Biomedical Applications, 2020
Neha Jain, Rajan Kumar Singh, R.A. Singh, Sudipta Som, Chung-Hsin Lu, Jai Singh
Luminescence originates from the electronic transition between 4f levels due to electric dipole and magnetic dipole interaction. Electric dipole interaction between free electrons of 4f valence shell is parity-forbidden, but it can be partially allowed by mixing of the orbital with a different parity. Electric dipole transition depends on site symmetry but magnetic dipole is not affected much (Malta et al. 1991). The selection rule for light emission is based on change in the total angular momentum of the electronic state as given below: Magnetic dipole transition ∆J = 0, ±1 (except for 0→0)Electric dipole transition ∆J = ±2
Quantum dynamics and spectra of the iodine atom in a strong laser field as calculated with the URIMIR package
Published in Molecular Physics, 2019
R. Marquardt, M. Quack, J. Stohner, I. Thanopulos
Consider a magnetic dipole moment of . In the Gaussian system of units, the magnetic dipole moment becomes . In the Gaussian system of units a magnetic dipole transition induced by a magnetic dipole moment of can thus be considered as an electric dipole transition induced by an electric dipole moment of , just weakened by the numerical factor . Because in the Gaussian system of units the electric field and the magnetic induction field have the same units, one can thus numerically treat magnetic dipole transitions as electric dipole transitions by including the numerical factor in the value of the magnetic dipole matrix element. In such a case, and for a given laser intensity, the value of the field instead of the value of the field is used in the numerical treatment; we however stress that the symmetry rules related to magnetic dipole transitions must be taken into account explicitly in the definition of the coupling matrix elements between the levels included in the numerical simulation.
1,10-Phenanthroline decorated with substituent groups forming europium(III) complexes: synthesis, crystal structure, photoluminescence properties and their bioimaging in living cells
Published in Journal of Coordination Chemistry, 2020
Huimin Song, Congbin Fan, Renjie Wang, Zheng Wang, Shouzhi Pu
The emission spectra of the two complexes exhibited characteristic red emission of Eu(III) ion at room temperature, while emission peaks were not observed for the ligand (Figures 4-6). Energy transfer was effective from the ligands to the central Eu ion. The luminescence spectra of the complexes in different solutions exhibit five characteristic 7Fj sharp peaks (j = 0, 1, 2, 3, 4) coming from the 5D0 emitting state of europium. It is simple to assign the acquired bands to suitable f–f transitions. Here, the five peaks at 580, 590, 615, 650 and 700 nm conform to the 5D0→7F0, 5D0→7F1, 5D0→7F2, 5D0→7F3 and 5D0→7F4 transitions, respectively [49, 50]. The emission spectra of the two compounds are dominated by an intense electric-dipole (5D0→7F2) transition, which led to strong emission of the two complexes Eu(tta)3L1 and Eu(tta)3L2. There are two weak emission peaks at 580 and 650 nm, which were ascribed to forbidden transitions in magnetic and electric dipoles of 5D0→7F0 and 5D0→7F3 transition. The 5D0→7F1 magnetic dipole transition has no connection with the coordination sphere, while the electric dipole transition 5D0→7F2 is susceptible to the nature and symmetry of the coordinating environment.
Luminescence properties of color-tunable YNbO4: Dy3+, Tm3+ phosphors
Published in Journal of Asian Ceramic Societies, 2020
Xin Wang, Xiangping Li, Sai Xu, Lihong Cheng, Jiashi Sun, Jinsu Zhang, Xizhen Zhang, Baojiu Chen
Dy3+ ion, as a luminescent center, has been widely studied in white-light illumination owing to its two characteristic emissions, respectively, locates at around 470 ~ 500 nm and 560 ~ 600 nm corresponding to 4F9/2→6H15/2 (magnetic dipole transition) and 4F9/2→6H13/2 (electric dipole transition) [8,10–12]. The transition intensities of the Dy3+ mainly depend on the host or the crystal-field environment. Usually, the electric dipole transition is hypersensitive to the surrounding environment, while the magnetic dipole transition is insensitive [6,13]. It is reported that when Dy3+ ions occupy at low symmetry sites with no inversion center, the yellow emission is dominated in the emission spectra [10,12,14]. Therefore, it is possible to achieve white-light emission from Dy3+ single-doped materials by adjusting the intensity ratio (Y/B) of yellow to blue emission. However, high-quality white light usually cannot be obtained by Dy3+ single-doped case owing to the deficiency of blue spectral component [15–17]. To solve this problem, an additional blue light-emitting center was usually introduced into Dy3+-activated systems to compensate for the insufficient blue light components. Tm3+ ion is a good blue light compensator because its transition 1D2→3F4 can emit blue emission centered at around 450 nm [18–21]. Moreover, it is also reported that there is an energy transfer between Tm3+ and Dy3+ under ultraviolet (UV) light excitation, and color-controllable emissions were obtained in Dy3+, Tm3+ co-doped phosphors by adjusting the concentrations of Tm3+ and Dy3+ [8,12].