Multiplet Manifolds Research Articles

Photoluminescence and energy transfer mechanisms of Tm3+ doped Y2O3 laser crystals: experimental and theoretical insights.

Rare-earth thulium (Tm3+) doped yttrium oxide (Y2O3) host single crystals are promising "eye-safe" laser materials. However, the mechanisms of photoluminescence and energy transfer in Tm3+ doped Y2O3 crystals are not yet understood at the fundamental level. Here, we synthetize a series of Y2O3:Tm3+ samples by the sol-gel method. Our experimental results show that the most intensive absorption line of the 3H6 → 1D2 transition occurs at 358 nm, and the strongest emission line of the 1D2 → 3F4 transition is located at 453 nm, which are in good agreement with the calculations of 363 nm and 458 nm, respectively. By using the CALYPSO structural search method, the ground state structure of Y2O3:Tm3+ with P2 space group symmetry is uncovered. The complete energy levels, including free-ion LS terms and crystal-field LSJ multiplet manifolds, of Y2O3:Tm3+ are obtained based on our developed WEPMD method. The present findings show that our WEPMD method can be used in experiments to elucidate the underlying mechanisms of photoluminescence and energy transfer in Tm3+ doped Y2O3 crystals, which offer insights for further understanding of other rare-earth doped laser materials.

Electronic Structure of Lr+ (Z = 103) from Ab Initio Calculations

The four-component relativistic Dirac–Coulomb Hamiltonian and the multireference configuration interaction (MRCI) model were used to provide the reliable energy levels and spectroscopic properties of the Lr+ ion and the Lu+ homolog. The energy spectrum of Lr+ is very similar to that of the Lu+ homolog, with the multiplet manifold of the 7s2, 6d17s1 and 7s17p1 configurations as the ground and low-lying excited states. The results are discussed in light of earlier findings utilizing different theoretical models. Overall, the MRCI model can reliably predict the energy levels and properties and bring new insight into experiments with superheavy ions.

Optical Transitions and Excited State Absorption Cross Sections of SrLaGaO4 Doped with Ho3+ Ions.

The spectroscopic properties of SrLaGaO4 (SLO) crystal doped with Ho3+ ions were studied in this work. Absorption, emission spectra and decay dynamics of excited states have been measured and discussed using the Judd–Ofelt model. Photoluminescence emissions were attributed to transitions from the excited 3D3, 5S2, 5F5, 5I6 and 5I7 multiplet manifolds. The experimental lifetimes for five excited states have been compared to the theoretical values, calculated using Judd–Ofelt theory, allowing for the determination of the multiphonon relaxation rates (WnR) of the respective states. The experimental data were approximately on a line expressed by WnR = W0 exp(−αΔE) with W0 = 0.5 × 107 s−1 and α = 2.6 × 10−3 cm. To discuss the excited state absorption (ESA) pathways, that originated from several excited levels, we used the Judd–Ofelt formalism allowing determination of the integrated cross section for ESA transitions.

Energy-level structure and spectral analysis of Nd3+ in GdNbO4 crystal

A detailed crystal-field splitting analysis is given for the 22 lowest-energy multiplet manifolds of Nd3+ (4f3) in GdNbO4 crystal. The absorption spectra obtained at room temperature, excitation spectra obtained at 8 K in the wavelength range of 280–900 nm, and emission spectra obtained between 8 K and room temperature in the wavelength range of 950–1420 nm are analyzed for transitions between individual energy (Stark) levels. Based on the excitation and absorption spectra, all of the 63 Stark levels associated with these manifolds are identified by transitions from the ground state Stark level 4I9/2 (Z1) to excited stark levels. Based on the emission spectra, the emitting stark level 4F3/2 (R1) to the stark levels in the manifolds of 4I9/2, 4I11/2 and 4I13/2 are obtained. The effective Judd-Ofelt parameters are calculated to be:6.126, 1.561, and 2.8071 × 10−20 cm2, respectively. All of the obtained energy level and spectroscopic parameters have great significance for the in-depth research of a new laser crystal of Nd:GdNbO4.

Optical spectroscopy of Dy3+ doped borate glasses for luminescence applications

Dy3+ ion embedded in (50−x)B2O3–20PbO–15MgF2–15NaCl–xDy2O3(x=0.2, 0.4, 0.6, 0.8, 1.0 and 2.0mol%) borate glasses are prepared and investigated using Differential Thermal Analysis (DTA), X-ray Diffractometer (XRD), Raman spectra, optical absorption and photoluminescence (PL) as function of different concentrations. Thermal stability of borate glass has been calculated from DTA profiles. The amorphous nature of glass matrix is confirmed by XRD. Based on Raman spectra, the functional groups that are present in the glass matrices have been analyzed. Based on the Judd–Ofelt theory, three spectral intensity parameters Ωλ (λ=2, 4, 6) are calculated from absorption spectra. These parameters are used to determine radiative transition probabilities (AR), radiative lifetimes (τR) and branching ratios (βR) of Dy3+ transitions from the excited state manifolds to corresponding lower laying multiplet manifolds. PL spectra show two intense and one weak band due to 4F9/2→6H15/2 (blue), 6H13/2 (yellow) and 6H11/2 (red) transitions respectively. For these transitions luminescence properties are studied. With the increase in the concentration of Dy3+ ions, intensity increases up to 0.8mol% and then concentration quenching is observed. This is (0.8mol%) the optimized concentration for the present prepared glasses. Lifetimes (τexp) are calculated for all the glass matrices from decay curve analysis. Spectroscopic and luminescence properties at 0.8mol% doped dysprosium ion are compared with other reported glass matrices. From the above analysis suggest that 0.8mol% of Dy3+ doped borate glasses can be useful for yellow lighting applications in the visible spectral region.

All homogeneous N = 2 M-theory truncations with supersymmetric AdS4 vacua

We study consistent truncations of M-theory to gauged N=2 supergravity in four dimensions, based on a large class of SU(3)-structures in seven dimensions. We show that the gauging involves isometries of the vector multiplet scalar manifold as well as the Heisenberg algebra and a special isometry of the hyperscalar manifold. As a result, non-abelian gauge groups and new non-trivial scalar potentials are generated. Then we specialize to all homogeneous SU(3)-structures supporting supersymmetric AdS4 vacua. These are the Stiefel manifold V52, the Aloff-Wallach spaces N(k,l), the seven-sphere (seen as SU(4)/SU(3) or Sp(2)/Sp(1)) and the M110 and Q111 coset spaces. For each of these cases, we describe in detail the N=2 model and discuss its peculiarities.

Analysis of the spectra of trivalent erbium in multiple sites of hexagonal aluminum nitride

The 12 K cathodoluminescence spectra of Er3+ doped into single crystals of aluminum nitride (2H-AlN) in the hexagonal phase are reported between 320 nm and 775 nm. The emission spectra represent transitions from the lower Stark level of 2P3/2 to the Stark levels of the 4I15/2, 4I13/2, 4I11/2, 4I9/2, 4F9/2, and 4S3/2 multiplet manifolds of Er3+(4f11). Emission spectra from 4S3/2 to 4I15/2 are also reported. All observed strong line emission are accounted for in terms of two principle sites, denoted site “a” and site “b”, with a few line spectra attributed to additional sites. A parameterized Hamiltonian that includes the atomic and crystal-field terms for Er3+(4f11)2S+1LJ was used to determine the symmetry and the crystal field splitting of the “a” and “b” sites. A descent in symmetry calculation was carried out to determine if distortion due to the size difference between Er, Al and the vacancies can be discerned. Modeling results assuming C3v and C1h are discussed. It appears that the sensitivity to a C1h model is not sufficient to invalidate the choice of C3v as an approximate symmetry for both sites. The g-factors reported from an EPR study of Er3+ in single-crystal AlN are in reasonable agreement with calculated g-factors for Er3+ in the “a” site assuming C3v symmetry.

Crystal field and Zeeman splittings for energy levels of Nd^3+ in hexagonal AlN

The crystal-field and Zeeman splittings of the energy levels of Nd3+(4f3) 2S+1LJ in hexagonal phase AlN have been investigated. The multiplet manifolds of Nd3+(4f3) analyzed include the ground state, 4I9/2, and excited states 4I11/2, 4I13/2, 4F3/2, 4F5/2, 2H(2)9/2, 4F7/2, 4S3/2, 4G5/2, and 2G7/2. Experimental energy levels were obtained from analyses of the 12 K cathodoluminescence spectra from Nd3+-implanted films of AlN, and from the 15 K photoluminescence excitation spectra and the site-selective combined excitation-emission spectra (CEES) recently reported for in situ Nd-doped hexagonal AlN grown by plasma-assisted molecular beam epitaxy (PA-MBE). CEES results identify a main site and two minority sites for Nd3+ in both samples. Transition line strengths attributed to the ion in minority sites are relatively stronger in Nd:AlN than in Nd:GaN. The 15 K experimental Zeeman splitting of Nd3+ are analyzed in the PA-MBE grown AlN samples and compared with the Zeeman splitting observed in Nd:GaN. The crystal-field and Zeeman splittings were modeled using a parametrized Hamiltonian consisting of atomic and crystal-field terms. We considered possible site distortion due to the size of the implanted Nd ion that would reduce the site symmetry from C3v to C3 or C1h. However, no significant improvement was obtained using these lower symmetry models, leading us to conclude that C3v symmetry is a reasonable approximation for the main site Nd3+ ions in AlN.

Magnetooptics of magnetic-dipole transitions in the rare-earth paramagnetic garnets

The Faraday effect (FE) of the rare-earth (RE) paramagnetic garnet crystals associated with magnetic-dipole (MD) transitions has been investigated theoretically over a wide temperature range 80 to 300 K. Over this temperature range, the “gyromagnetic” Verdet Vgm(m) of the Eu3Ga5O12 (EuGG) is not a linear function of the magnetic susceptibility χ measured along the [111] axis. We find that the nontrivial character of the temperature dependence of the MD Verdet constant Vgm(m) is associated with the presence of a contribution to the Faraday rotation of the Van Vleck “mixing” by an external magnetic field of the Eu3+ electronic states. The optical absorption and magnetic circular dichroism (MCD) of Eu3+ ion in EuGG at 85 K for the MD transition 7F0 → 5D1 were measured along the [111] axis. We show that the appearance of the MCD feature observed for the absorption line near 526.6 nm for the 7F0 → 5D1 MD absorption band may be well-explained by the contribution of Van Vleck “mixing” between the Stark singlet states from the 7F0 and 7F1 multiplet manifolds mixed by the external magnetic field H.

Crystal-field analysis and Zeeman splittings of energy levels of Nd3+ (4f3) in GaN

The crystal-field splitting and Zeeman splitting of energy levels of Nd3+ (4f3) doped into semi-conducting GaN (3.2 eV) grown in the hexagonal (huntite) phase by plasma-assisted molecular beam epitaxy have been modeled using a parameterized Hamiltonian defined to operate within the complete 4f3 electronic configuration of Nd3+ substituted for Ga3+ in the lattice. Zeeman splittings were obtained by applying magnetic fields up to 6.6 T with the fields parallel and perpendicular to the crystallographic c-axis. The experimental energy (Stark) levels were obtained from a recent spectroscopic study on the same samples, where the combined excitation emission spectroscopy (CEES) identified the majority of Nd3+ ions as replacing Ga3+ in sites of C3v symmetry. The manifolds of Nd3+ (4f3)2S+1LJ modeled for the crystal-field splitting include the ground state, 4I9/2, and excited states 4I11/2, 4I13/2, 4F3/2, 4F5/2, 2H9/2, 4F7/2, 4S3/2, 4G5/2, and 4G7/2. The energies of 41 experimental Stark levels from these manifolds were modeled through the use of a Monte Carlo method in which independent crystal-field parameters (CFP) were given random starting values and optimized using standard least-squares fitting between calculated and experimental Stark levels. Irreducible representations (irreps) and crystal field quantum numbers (μ) were assigned to the energy level states of the 4I9/2 and 4F3/2 multiplet manifolds based on an analysis of the Zeeman data. This allows determination of which of the competing local minima should be considered to be the physically significant minimum. Using standard least-squares fitting between calculated and experimental Stark levels for Nd3+ in C3v symmetry, we obtain a final standard deviation of 7.01 cm−1 (rms = 5.48 cm−1).

Spectra, energy levels, and symmetry assignments for Stark components of Eu 3+(4f 6) in gadolinium gallium garnet (Gd 3Ga 5O 12)

Absorption and fluorescence spectra observed between 450 and 750 nm at 85 K and room temperature (300 K) are reported for Eu 3+(4f 6) in single-crystal Czochralski-grown garnet, Gd 3Ga 5O 12 (GGG). The spectra represent transitions between the 2 S+1 L J multiplets of the 4f 6 electronic configuration of Eu 3+ split by the crystal field of the garnet. In absorption, Eu 3+ transitions are observed from the ground state, 7F 0, and the first excited multiplet, 7F 1, to multiplet manifolds 5D 0, 5D 1, and 5D 2. The Stark splitting of the 7F J multiplets ( J=0–6) was determined by analyzing the fluorescence transitions from 5D 0, 5D 1, and 5D 2 to 7F J . The Eu 3+ ions replace Gd 3+ ions in sites of D 2 symmetry in the lattice during crystal growth. Associated with each multiplet manifold are 2 J+1 non-degenerate Stark levels characterized by one of four possible irreducible representations (irreps) assigned by an algorithm based on the selection rules for electric-dipole (ED) and magnetic-dipole (MD) transitions between Stark levels in D 2 symmetry. The quasi-doublet in 5D 1 was characterized by an analysis of the magneto-optical spectra obtained from the transitions observed between 5D 1 and 7F 1. A parameterized Hamiltonian defined to operate within the entire 4f 6 electronic configuration of Eu 3+ was used to model the experimental Stark levels and their irreps. The crystal-field parameters were determined through use of a Monte-Carlo method in which nine independent crystal-field parameters, B q k , were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviation between 57 calculated-to-experimental Stark levels is 5.9 cm −1. The choice of coordinate system, in which the nine B q k are real and the crystal-field z-axis is parallel to the [0 0 1] crystal axis and perpendicular to the xy plane, is identical to the choice we used previously in analyzing the spectra of Er 3+ and Ho 3+ garnets.

Analyses of the ultraviolet spectra of Er3+ in Er2O3 and Er3+ in Y2O3

The ultraviolet (uv) absorption spectra, representing transitions to all energy levels below 44 500 cm−1 of trivalent erbium (Er3+), have been analyzed for the crystal-field splitting of the multiplet manifolds L2S+1J of Er3+(4f11) in C2 symmetry cation sites in single-crystal cubic Er2O3 and Er3+:Y2O3. A solid solution, without a change in the local symmetry, exists between the two compounds, allowing us to identify the weaker transitions in Er3+:Y2O3 from the stronger transitions observed in the uv spectrum of Er2O3. As a result, we have identified a complete set of energy (Stark) levels for the electronic configuration up to the absorption band-edge of these crystals. A total of 134 Stark levels representing 30 multiplets with energies as high as 44 500 cm−1 have been modeled using a parameterized Hamiltonian defined to operate within the Er3+(4f11) electronic configuration. The crystal-field parameters were determined through use of a Monte Carlo method in which 14 independent crystal-field parameters, Bqk, were given random starting values and optimized using standard least-squares fitting between calculated and experimental levels. The final fitting standard deviations between 134 calculated-to-experimental Stark levels are 5.55 cm−1 (rms error 4.89 cm−1) and 5.08 cm−1 (rms error 4.47 cm−1) for Er3+ in Er2O3 and for Er3+ in Y2O3, respectively. The excellent and consistent agreement between the experimental and calculated Stark levels in both crystals, together with the predicted sets of wave functions, are important for the ongoing analyses of intensity data and magneto-optical studies on these crystals.

Spectra and energy levels of Eu3+ in cubic phase Gd2O3

In pulsed laser deposition of the sesquioxide semiconductor Gd2O3, adjusting the chamber oxygen pressure controls the crystalline structure of the host. This technique was used to deposit thin films of nominally 1.6% by weight europium-doped, cubic phase Gd2O3 using 50 mTorr of oxygen. Structural measurements using high-resolution transmission electron microscopy and selected area electron diffraction confirm the films were polycrystalline, cubic phase Eu:Gd2O3. The spectroscopic assignment of emission lines to specific radiative transitions within the trivalent Eu ion is confirmed by theoretical analysis of the appropriate crystal field Hamiltonian. Detailed crystal-field splittings are presented for the 5DJ=0-2 and 7FJ=0-5 multiplet manifolds of Eu3+ in this host material.

Analyses of 4f11 Energy Levels and Transition Intensities Between Stark Levels of Er3+ in Y3Al5O12

ABSTRACT Absorption and fluorescence spectra obtained at temperatures as low as 4 K were investigated between 200 and 1550 nm on samples containing approximately 1.2 at. wt. % Er in Y3Al5O12 (YAG). Within this wavelength range 125 experimental energy (Stark) levels were analyzed, representing data that span 29 2S+1 L J multiplet manifolds of Er3+(4f11) in D2 sites up to an energy of 44,000 cm−1. Agreement between calculated and observed Stark levels was achieved with an r.m.s. deviation of 11.2 cm−1. These transitions originate from the ground-state Stark level in the 4I15/2 manifold to J + 1/2 Stark levels associated with each of the 28 excited-state manifolds. A total of 88 ground-state absorption transition line strengths were measured for 19 2S+1 L J multiplet manifolds between 280 and 1550 nm. For line strength measurements, the Er3+ ion is assumed to be distributed homogeneously throughout the D2 cation sites of Y3+ in the lattice. The line strengths were analyzed with a weighted (E i − C i )/E i , with an r.m.s. error of 0.25. Use of a “vector crystal field” parametrization resolves ambiguities in the transition intensity parameters and allows for the definition of polarization-resolved Judd-Ofelt parameters, which may have wide-ranging applicability for future Judd-Ofelt-type intensity calculations.

Energy levels and symmetry assignments for Stark components of Ho3+(4f10) in yttrium gallium garnet (Y3Ga5O12)

Absorption and fluorescence spectra observed between 1950 and 320 nm at sample temperatures of 8, 78, and 293 K, representing more than 900 transitions between 24 multiplets L2S+1J of Ho3+(4f10) split by the crystal field, have been analyzed in Czochralski-grown single crystals of Ho3+ doped-yttrium gallium garnet (Y3Ga5O12 or YGG). The Ho3+ ions replace Y3+ ions in sites of D2 symmetry during crystal growth. Associated with each multiplet manifold are 2J+1 nondegenerate crystal-field split sublevels (Stark levels) characterized by one of four different irreducible representations (irreps) associated with D2 symmetry. The energy and irrep assignments for individual experimental Stark levels were established by an algorithm that makes use of the selection rules for electric-dipole (ED) and magnetic-dipole (MD) transitions between Stark levels. Nearly degenerate Stark levels (quasidoublets) in several manifolds have been observed and investigated by magneto-optical methods reported in a separate study. Of the 252 predicted Stark levels associated with the 24 multiplet manifolds, 241 were experimentally determined of which 161 had symmetry irreps unambiguously identified by the algorithm method and confirmed by crystal-field modeling studies. A final least-squares fitting between 241 calculated-to-experimental Stark levels was obtained with a standard deviation of 4.86 cm−1 (rms error of 4.60 cm−1). The algorithm works best for identifying irreps when neighboring excited Stark levels are sufficiently separated so that a pattern of temperature-dependent (“hot band”) transitions can be unambiguously associated with each excited Stark level.

Absorption intensities, emission cross sections, and crystal field analysis of selected intermanifold transitions of Ho3+ in Ho3+:Y2O3 nanocrystals

Optical absorption and emission intensities are investigated for Ho3+ in nanocrystalline Ho3+:Y2O3. Room temperature absorption intensities of Ho3+(4f10) transitions in synthesized Ho3+:Y2O3 nanocrystals have been analyzed using the Judd–Ofelt (JO) approach to obtain the phenomenological intensity parameters Ω2, Ω4, and Ω6. The JO intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Ho3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Ho3+(4f10). The emission cross sections of the intermanifold transitions F54,S52→I58 (0.549 μm) and I56→I58 (1.204 μm) have been determined. The room temperature fluorescence lifetimes of these transitions in Ho3+:Y2O3 nanocrystals were measured. Radiative and fluorescence lifetimes are used to determine the quantum efficiency. The low temperature spectra are analyzed for the energy (Stark) level transitions of select L2S+1J multiplet manifolds of Ho3+(4f10). The comparative study of Ho3+(4f10) ions suggests that synthesized Ho3+:Y2O3 nanocrystals could be an excellent alternative to single-crystal Ho3+:Y2O3 for certain photonic applications, especially in the near infrared region.

Intensity analysis and energy-level modeling of Nd3+ in Nd3+:Y2O3 nanocrystals in polymeric hosts

Optical absorption and emission intensities are investigated for Nd3+ in nanocrystalline Nd3+:Y2O3. Room temperature absorption intensities of Nd3+(4f3) transitions in synthesized Nd3+:Y2O3 nanocrystals have been analyzed using the Judd–Ofelt (J-O) approach to obtain the phenomenological intensity parameters. The J-O intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Nd3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Nd3+(4f3). The emission cross sections and room temperature fluorescence lifetimes of the important intermanifold F43/2→I4J (J=9/2,11/2,13/2,15/2) transitions have been determined. We also compare the spectra of the Nd3+:Y2O3 nanocrystals to those of the nanocrystals embedded in polymeric matrices of epoxy and chitosan, and we find similarities in terms of the detailed Stark energy levels of the Nd3+ ion in the Y2O3 nanocrystalline host. The 300 K spectra are analyzed for the energy (Stark) level transitions between the L2S+1J multiplet manifolds of Nd3+(4f3). The results of this study are also compared with a crystal-field splitting analysis reported earlier for single-crystal Nd3+:Y2O3 grown by a modified flame fusion method. We find that the spectroscopic properties of our nanocrystals embedded in polymeric hosts compare favorably with other ceramic and single-crystal forms of Nd3+:Y2O3 currently available.

Optical intensity analyses of Er3+:YAlO3

Analyses of the optical absorption and emission intensities are performed on Er3+ ions doped into yttrium orthoaluminate YAlO3 to assess this material as a laser source. The Judd–Ofelt model is applied to the room temperature absorption intensities of Er3+ in YAlO3 to obtain the phenomenological intensity parameters: Ω2=1.06×10−20 cm2, Ω4=1.96×10−20 cm2, and Ω6=1.40×10−20 cm2. The intensity parameters are used to determine the radiative decay rates and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Er3+ in YAlO3. Using the radiative decay rates, radiative lifetimes of 13 excited states have been determined. The room temperature fluorescence lifetime of the Er3+ S43/2→I415/2 transition is measured to be 0.43 ms. Values of emission cross section and peak emission cross section have been obtained for the Er3+ I413/2→I415/2 and S43/2→I415/2 intermanifold transitions. The detailed structure observed in the manifold-to-manifold transitions allows us to identify the Stark splitting of the individual manifolds.

Modeling optical transitions of Er3+(4f11) in C2 and C3i sites in polycrystalline Y2O3

The optical properties of Er3+ in polycrystalline (ceramic), and nanocrystalline forms of cubic (bixbyite) yttrium oxide are modeled based on the absorption spectra obtained between 400 and 1700 nm and the fluorescence spectra observed between 1500 and 1670 nm. Both spectra were obtained at 8 K. The observed crystal-field splitting and the measured intensities of transitions between Stark levels of the L2S+1J multiplet manifolds of Er3+(4f11) in both the C2 and C3i sites of Y2O3 are analyzed in terms of established models. The inversion symmetry of C3i sites limits the observed electronic transitions to magnetic dipole transitions between the I413/2 and I415/2 manifolds. There is no spectroscopic evidence for transitions involving other multiplet manifolds of Er3+ ions in C3i sites. For Er3+ ions in C2 sites, forced electric dipole transitions are allowed between the J+12 Stark levels associated with each manifold. With few exceptions, the crystal-field splitting and the intensities of the transitions between Stark levels are comparable between the nanocrystalline, polycrystalline, and the flame fusion grown crystals of cubic yttrium oxide containing trivalent erbium.

Intensity analysis and crystal-field modeling of Ho3+ in KPb2Cl5 host

Optical absorption and emission intensities are investigated for Ho3+ doped into single-crystal KPb2Cl5. Room temperature absorption spectra of Ho3+(4f10), representing transitions from I58 to excited multiplet manifolds observed between 400 and 2100 nm, have been analyzed using the Judd–Ofelt (JO) model to obtain the phenomenological intensity parameters Ω2, Ω4, and Ω6. The JO intensity parameters are used to calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios of the Ho3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds L2S+1J of Ho3+. The room temperature fluorescence spectrum in the near infrared region is reported between 850 and 1550 nm. The emission cross section for the intermanifold transition, F55→I57 (0.98 μm) has been determined. The 8 K absorption spectrum was examined as well. The detailed structure observed in the absorption bands I57, S52, F54, and F53, was analyzed in terms of the crystal-field splitting of each manifold using a charge-compensation model first developed for Er3+ doped into KPb2Cl5. The optical and spectroscopic characteristics of Ho3+:KPb2Cl5 demonstrate that this material has potential as a laser host system at various wavelengths.