Largest eigenvalue distribution in the double scaling limit of matrix models: A Coulomb fluid approach

Using thermodynamic arguments we find that the probability that there are no eigenvalues in the interval (-s,\infty) in the double scaling limit of Hermitean matrix models is O(exp(-s^{2m+1})) as s\to+\infty.Here m=1,2,3.. determine the m^{th} multi-critical point of the level density:\sigma(x)\sim b[1-(x/b)^2]^{m-1/2} and b^2\sim N.Furthermore,the size of the transition zone where the eigenvalue density becomes vanishingly small at the tail of the spectrum is \sim N^{(m-3/2)/(2m+1)} in agreement with earlier work based on the string equation.Comment: 10 pages, no figures, to appear in J.Phys. A Lett. 199

Oxide phosphors for light upconversion; Yb3+ and Tm3+ co-doped Y2BaZnO5

Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 109, 063104 (2011) and may be found at

The total energy splitting of ionic eigenstates in the axial crystal fields

The relationship between the energy total splitting $\Delta E$ of the free-ion electron states in the axial crystal-fields and the second moment of that splitting $\sigma^{2}$ is thoroughly investigated. The non-Kramers and Kramers states with the quantum number $1\leq J \leq 8$ in the axial crystal-fields of any multipolar composition but fixed $\sigma^{2}$ are considered. Since the crystal-field Hamiltonian ${\cal H}_{\rm CF}$ is a superposition of the three effective multipoles various $\Delta E$ can correspond to a fixed $\sigma^{2}$ according to the resultant combination of the independent contributions. This $\Delta E$ variation range is the subject of the study. For the states under examination $\Delta E$ can take the values from $2.00\sigma$ to $3.75\sigma$, whereas the difference $\Delta E_{max}- \Delta E_{min}$, except the states with $J\leq 5/2$, amounts roughly to $\sigma$. For comparison, the one-multipolar ${\cal H}_{\rm CF}$s yield accurately defined $\Delta E$ ranging from $2.50\sigma$ to $3.00\sigma$. The limitations of the allowed $\Delta E$ values exclude rigorously a number of virtually possible splitting diagrams. The documentary evidence for this restriction has been supplied in the paper collating the nominally admissible total energy splittings $\Delta {\cal E}$ (i.e. those preserving the $\sigma^{2}$) with the $(\Delta E_{min}, \Delta E_{max})$ ranges occurring in the actual axial crystal-fields. Although the $\Delta E$ unlike the $\sigma^{2}$ is not an essential characteristic and depends on the reference frame orientation, it is useful to know its dispersion range, particularly attempting to assign or verify complex electron spectra.Comment: 17 pages, 4 tables, submitted to pss(b

The limits of the total crystal-field splittings

The crystal-fields causing $|J>$ electron states splittings of the same second moment $\sigma^{2}$ can produce different total splittings $\Delta E$ magnitudes. Based on the numerical data on crystal-field splittings for the representative sets of crystal-field Hamiltonians ${\cal H}_{\rm CF}=\sum_{k}\sum_{q}B_{kq}C_{q}^{(k)}$ with fixed indexes either $k$ or $q$, the potentials leading to the extreme $\Delta E$ have been identified. For all crystal-fields the admissible ranges $(\Delta E_{min},\Delta E_{max})$ have been found numerically for $1\leq J\leq 8$. The extreme splittings are reached in the crystal-fields for which ${\cal H}_{\rm CF}s$ are the definite superpositions of the $C_{q}^{(k)}$ components with different rank $k=2,4$ and 6 and the same index $q$. Apart from few exceptions, the lower limits $\Delta E_{min}$ occur in the axial fields of ${\cal H}_{\rm CF}(q=0)=B_{20}C_{0}^{(2)}+B_{40}C_{0}^{(4)}+B_{60}C_{0}^{(6)}$, whereas the upper limits $\Delta E_{max}$ in the low symmetry fields of ${\cal H}_{\rm CF}(q=1)=B_{21}C_{1}^{(2)}+B_{41}C_{1}^{(4)}+B_{61}C_{1}^{(6)}$. Mixing the ${\cal H}_{\rm CF}$ components with different $q$ yields a secondary effect and does not determine the extreme splittings. The admissible $\Delta E_{min}$ changes with $J$ from $2.00\sigma$ to $2.40\sigma$, whereas the $\Delta E_{max}$ from $2.00\sigma$ to $4.10\sigma$. The maximal gap $\Delta E_{max}-\Delta E_{min}=2.00\sigma$ has been found for the states $|J=4>$. Not all the nominally allowed total splittings, preserving $\sigma^{2}=const$ condition, are physically available, and in consequence not all virtual splittings diagrams can be observed in real crystal-fields.Comment: 30 pages, Appendix (8 pages) and 11 tables; submitted to pss(b

U3+/LiYF4, a promising IR laser

Under reducing conditions, single crystal of LiYF4 doped with 762 ppm of U3+ were obtained. Absorption and fluorescence spectra of this system are presented as well as the energy level scheme of the lasing transition. Oscillator strength and laser cross section between Stark levels of the [MATH] transition are calculated

Novel Tm3+-doped fluorotellurite glasses with enhanced quantum efficiency

In this paper, new highly Tm3+-doped tellurite glasses with host composition 75TeO2-xZnF2-yGeO2-12PbO-3Nb2O5 [x(5-15), y(0-5) mol%] are presented and compared to the Tm-doped tellurite glasses based on the traditional host composition: 75TeO2-20ZnO-5Na2O mol%. Enhanced quantum efficiency from 3F4 level was observed for the proposed glasses and thermal stability and viscosity values make them suitable for optical fiber drawing. Besides the host composition, substantial influence of Tm3+ concentration on luminescence and lifetime of excited 3F4 and 3H4 states were discusse

Synthesis, structure and luminescence of Er3+-doped Y3Ga5O12 nano-garnets

A novel Y3(1-x)Er3xGa5O12 nanocrystalline garnet has been synthesized by a sol-gel technique and a complete structural, morphological, vibrational, and optical characterization has been carried out in order to correlate the local structure of the Er3+ ions with their optical properties. The synthesized nanocrystals are found in a single-phase garnet structure with an average grain size of around 60 nm. The good crystalline quality of the garnet structure is confirmed by FTIR and Raman measurements, since the phonon modes of the nano-garnet are similar to those found in the single crystal garnet. Under blue laser excitation, intense green and red visible and 1.5 mu m infrared luminescences are observed, whose relative intensities are very sensitive to the Er3+ concentration. The dynamics of these emissions under pulsed laser excitations are analyzed in the framework of different energy transfer interactions. Intense visible upconverted luminescence can be clearly observed by the naked eye for all synthesized Er3+-doped Y3Ga5O12 nano-garnets under a cw 790 nm laser excitation. The power dependency and the dynamics of the upconverted luminescence confirm the existence of different two-photon upconversion processes for the green and red emissions that strongly depend on the Er3+ concentration, showing the potential of these nano-garnets as excellent candidates for developing new optical devices.This work has been partially supported by Ministerio de Ciencia e Innovacion of Spain (MICCIN) under The National Program of Materials (MAT2010-21270-C04-02; -03; -04), The Consolider-Ingenio 2010 Program (MALTA CSD2007-0045), and The National Infrastructure Program, by Ministerio de Economia y Competitividad of Spain (MINECO) within The Indo-Spanish Joint Programme of Cooperation in Science and Technology (PRI-PIBIN-2011-1153/DST-INT-Spain-P-38-11), and by the EU-FEDER funds (UCAN08-4E-008). S.F. Leon-Luis and V. Monteseguro wish to thank MICINN for the FPI grants (BES-2008-003353 and BES-2011-044596). Dr V. Venkatramu is grateful to DAE-BRNS, Government of India for the award of DAE Research Award for Young Scientists (no. 2010/20/34/5/BRNS/2223).Venkatramu, V.; León-Luis, SF.; Rodriguez-Mendoza, UR.; Monteseguro, V.; Manjón, FJ.; Lozano-Gorrín, AD.; Valiente, R.... (2012). Synthesis, structure and luminescence of Er3+-doped Y3Ga5O12 nano-garnets. Journal of Materials Chemistry. 22:13788-13799. doi:10.1039/c2jm31386cS13788137992

Thermal Scanning at the Cellular Level by an Optically Trapped Upconverting Fluorescent Particle

Single particle spectroscopy in the form of three-dimensional optical manipulation of an upconverting nanoparticle is here used for non-invasive thermal sensing at the cellular level. In particular, a single infrared 980 nm laser beam is used as a three-dimensional optical tweezer and, simultaneously, as an optical excitation source for a single NaYF4:Er3+,Yb3+ upconverting particle. Real time analysis of the thermosensitive green emission of Er3+ ions obtained after Yb3+ excitation provides thermal sensing during optical manipulation. Thus, three-dimensional particle scanning allows for the measurement of thermal gradients in the surroundings of individual cancer cells subjected to a plasmonic-mediated photothermal therapy. It is found that such thermal gradients extends for distances larger than 10 microns, avoiding real single cell photothermal treatments under in vitro conditions. This work introduces to the scientific community a novel and simple approach for high resolution thermal sensing at the cellular level that could constitute a powerful tool for a better understanding of cell dynamics during thermal treatmentsThis work was supported by the Spanish Ministerio de Educación y Ciencia (MAT2013–47395-C4–1-R) and by Banco Santander for “Proyectos de Cooperación Interuniversitaria” (2015/ASIA/06). P.H.G thanks the Spanish Ministerio de Economía y Competitividad (MINECO) for the Juan de la Cierva program. P.R.S thanks the Spanish Ministerio de Economía y Competitividad (MINECO) for the “Promoción del talento y su Empleabilidad en I+D+i” statal progra

Risk to Human Health from a Plethora of Simian Immunodeficiency Viruses in Primate Bushmeat

To assess human exposure to Simian immunodeficiency virus (SIV) in west central Africa, we looked for SIV infection in 788 monkeys that were hunted in the rainforests of Cameroon for bushmeat or kept as pets. Serologic reactivity suggesting SIV infection was found in 13 of 16 primate species, including 4 not previously known to harbor SIV. Overall, 131 sera (16.6%) reacted strongly and an additional 34 (4.3%) reacted weakly with HIV antigens. Molecular analysis identified five new phylogenetic SIV lineages. These data document for the first time that a substantial proportion of wild monkeys in Cameroon are SIV infected and that humans who hunt and handle bushmeat are exposed to a plethora of genetically highly divergent viruses