Optical spectra and thermal Schottky levels in dysprosium sesquisulfide

We report a detailed crystal-field splitting analysis of the energy levels of Dy3+(4f9)Dy3+(4f9) in single crystals of Dy2S3Dy2S3 that have the Th3P4Th3P4 cubic defect structure. From an analysis of the temperature-dependent absorption spectra, we have identified seven of the eight crystal-field split energy (Stark) levels of the ground-state multiplet manifold, 6H15/2.6H15/2. Sixty-two experimental Stark levels from various multiplet manifolds of Dy3+Dy3+ are compared with a calculated crystal-field splitting, whose initial crystal-field parameters, Bnm,Bnm, were determined from lattice-sum calculations. The rms deviation between experimental and calculated levels is 7 cm−1. Both the experimental and calculated crystal-field splitting of the 6H15/26H15/2 manifold are compared with an assignment of Schottky levels obtained from a reassessment of heat capacity data reported earlier. Based on entropy considerations and verification of the Schottky level assignments by analyses of the optical and magnetic susceptibility data, we conclude that the anomaly observed in the heat capacity data near 3.4 K is due to antiferromagnetic ordering. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69677/2/JCPSA6-110-24-12125-1.pd

Thermophysical properties of the lanthanide sesquisulfides. III. Determination of Schottky and lattice heat‐capacity contributions of γ‐phase Sm2S3 and evaluation of the thermophysical properties of the γ‐phase Ln2S3 subset

We report the experimental heat capacity of γ‐phase Sm2S3 and derived thermophysical properties at selected temperatures. The entropy, enthalpy increments, and Gibbs energy function are 21.50R, 3063R⋅K, and 11.23R at 298.15 K. The experimental heat capacity is made up of lattice and electronic (Schottky) contributions. The lattice contribution is determined for all γ‐phase lanthanide sesquisulfides (Ln2S3 ) using the Komada/Westrum model. The difference between the experimental heat capacity and the deduced lattice heat capacity is analyzed as the Schottky contribution. Comparisons are made between the calorimetric Schottky contributions and those determined based on crystal‐field electronic energy levels of Ln3+ ions in the lattice and between the Schottky contributions obtained from the empirical volumetric priority approach and from the Komada/Westrum theoretical approach. Predictions for the thermophysical properties of γ‐phase Eu2S3 and γ‐phase Pm2S3 (unavailable for experimental determination) are also presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71137/2/JCPSA6-96-8-6149-1.pd

Thermophysical properties of the lanthanide sesquisulfides. IV. Schottky contributions, magnetic, and electronic properties of ϵ‐phase Yb2S3 and Lu2S3

The heat capacities of ϵ‐phase Yb2S3 and Lu2S3 have been determined from 6 to 350 K and their thermodynamic properties evaluated. The resolution of the Schottky and magnetic properties by evaluation of the lattice heat capacity is shown to be in accord with spectroscopically determined energy levels. The lattice heat capacity of Yb2S3 was determined by means of the Komada–Westrum phonon distribution model. Excess heat‐capacity contributions were thus evaluated and analyzed as Schottky and magnetic heat capacities. A phase transition associated with magnetic ordering was detected in the heat capacity of Yb2S3 near 7 K with an entropy content of 0.68R. The entropies at 298.15 K are 22.77R and 19.74R for Yb2S3 and for Lu2S3.  Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70016/2/JCPSA6-98-2-1458-1.pd

Crystal field analysis of Pm3+^{3+} (4f4)andSm^{f4}) and Sm^{3+}(4 (4^{f5}) and lattice location studies of 147^{147}Nd and 147^{147}Pm in w-AlN

We report a detailed crystal field analysis of Pm3+ and Sm3+ as well as lattice location studies of 147Pm and 147Nd in 2H-aluminum nitride (w-AlN). The isotopes of mass 147 were produced by nuclear fission and implanted at an energy of 60 keV. The decay chain of interest in this work is 147Nd→147Pm→147Sm (stable). Lattice location studies applying the emission channeling technique were carried out using the β− particles and conversion electrons emitted in the radioactive decay of 147Nd→147Pm. The samples were investigated as implanted, and also they were investigated after annealing to temperatures of 873 K as well as 1373 K. The main fraction of about 60% of both 147Pm as well as 147Nd atoms was located on substitutional Al sites in the AlN lattice; the remainder of the ions were located randomly within the AlN lattice. Following radioactive decay of 147Nd, the cathodoluminescence spectra of Pm3+ and Sm3+ were obtained between 500 nm and 1050 nm at sample temperatures between 12 K and 300 K. High-resolution emission spectra, representing intra-4f electron transitions, were analyzed to establish the crystal-field splitting of the energy levels of Sm3+ (4f5) and Pm3+ (4f4) in cationic sites having C3v symmetry in the AlN lattice. Using crystal-field splitting models, we obtained a rms deviation of 6 cm−1 between 31 calculated-to-experimental energy (Stark) levels for Sm3+ in AlN. The results are similar to those reported for Sm3+ implanted into GaN. Using a set of crystal-field splitting parameters Bnm, for Pm3+ derived from the present Sm3+ analysis, we calculated the splitting for the 5F1, 5I4, and 5I5 multiplet manifolds in Pm3+ and obtained good agreement between the calculated and the experimental Stark levels. Temperature-dependent lifetime measurements are also reported for the emitting levels 4F5∕2 (Sm3+) and 5F1 (Pm3+)

The Strayed Reveller, No. 1

The Strayed Reveller is a literary magazine of stories, songs, poems, essays, reviews and artwork by students at Stephen F. Austin State University. It is published monthly andsponsered by the School of Liberal Arts and Department of English.https://scholarworks.sfasu.edu/reveller/1000/thumbnail.jp

Low-temperature heat capacities, thermophysical properties, optical spectra, and analysis of Schottky contributions to Pr(OH)3

From values of the heat capacity of microcrystalline Pr(OH)3 determined by precise adiabatic calorimetry from 15 to 350 K, the Schottky contribution associated with all but the lowest Stark level was resolved with the aid of a model of the lattice heat capacity based upon the molar volumes of the lanthanide trihydroxides. Visible and infrared absorption spectra were taken at approximately 95 K on microcrystalline mulls and the energy-level scheme and crystalline electric-field parameters evaluated. The Schottky contribution of all levels above the first excited state ([mu] = 3) was resolved by a new scheme for modeling the lattice contribution and compared with the same contribution deduced from the spectral results. Excellent accord was observed. These results together with magnetic results and the first excited Stark level were used to adjust the low-temperature heat capacities and thermodynamic functions so as to evaluate Cp/R, So/R, and - {Go - Ho(0)}/RT, at 298.15 K as 14.154, 15.84, and 7.766, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23751/1/0000724.pd

Thermophysical properties of the lanthanide sesquisulfides. II. Schottky contributions and magnetic and electronic properties of γ‐phase Pr2S3, Tb2S3, and Dy2S3

Heat‐capacity measurements by adiabatic equilibrium calorimetry are reported for γ‐phase Pr2S3, Tb2S3, and Dy2S3 between 5 and 350 K. Highly purified samples were prepared and their composition verified by chemical analysis. Precision lattice parameters were determined for each compound and are compared with literature values. The total heat capacity has been resolved into lattice, magnetic, and Schottky components by a volumetric approach. The experimental Schottky contributions accord with the calculated curves based on the crystal‐field splitting of the 2S+1LJ ground state of the lanthanide ions occupying sites of S4 symmetry in the Th3P4 lattice. The individual crystal‐field electronic energy levels have been obtained in part from an analysis of the hot‐band data observed in the absorption spectra of Pr2S3, Tb2S3, and Dy2S3, and from a calculated splitting in which the crystal‐field parameters Bkm, were determined from a lattice‐sum calculation. Molar thermodynamic properties are reported for all three compounds. The entropy at 298.15 K {S0−S0 (7 K)}, is 22.78R, 22.93R, and 23.36R, for γ‐phase Pr2S3, Tb2S3, and Dy2S3, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70592/2/JCPSA6-95-3-1964-1.pd

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 2P(3/2) to the Stark levels of the 4I(15/2), 4I(13/2), 4I(11/2), 4I(9/2), 4F(9/2), and 4S(3/2) multiplet manifolds of Er3+(4f(11)). Emission spectra from 4S(3/2) to 4I(15/2) 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+(4f(11)) (2S+1)L_J 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 C_3v and C_1h are discussed. It appears that the sensitivity to a C_1h model is not sufficient to invalidate the choice of C_3v 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 C_3v symmetry

Site-Selective Excitation And Polarized Absorption Spectra Of Nd3+ In Sr-5(Po4)(3)F And Ca-5(Po4)(3)F

Polarized absorption and fluorescence spectra were analyzed to establish individual energy (Stark) levels of Nd3+ ions in host crystals of Sr-5(PO4)(3)F (SFAP) and Ca-5(PO4)(3)F (FAP). Site-selective excitation and fluorescence facilitated differentiation between Nd3+ ions in emitting sites-associated with 1.06 mu m stimulated emission, and nonemitting Nd3+ ions in other sites. Measurements were made on samples containing different concentrations of Nd3+ at 4 K and higher temperatures. Substitution of Nd3+ for Sr2+ or Ca2+ was accompanied by passive charge compensation during crystal growth. Crystal-field splitting calculations were performed according to site for Stark levels of Nd3+ ions identified spectroscopically. We obtained a final set of crystal-field parameters B-nm for Nd3+ ions in fluorescing sites with a rms, deviation of 7 cm(-1) (52 levels in Nd:SFAP) and 8 cm(-1) (59 levels in Nd:FAP). For one of the nonemitting sites in Nd:FAP we obtained a final set of B-nm parameters which gave a rms deviation of 6 cm(-1) between 46 experimental and calculated levels