Optical Spectroscopy

Analysis of Optical Absorbance Spectra for the Determination of ZnO Nanoparticle Size Distribution, Solubility, and Surface Energy

by Robin Klupp Taylor

Large-scale first principles configuration interaction calculations of optical absorption in boron clusters

by Ravindra Shinde

In the whirlpool's coils: tracing substructure from combined optical/X-ray data in the galaxy cluster A1300

by Felicia Ziparo

F. Ziparo, F.G. Braglia, D. Pierini, A. Finoguenov, H. Boehringer, A. Bongiorno

Structure formation is thought to act via hierarchical mergers and accretion of smaller systems driven by gravity with... more Structure formation is thought to act via hierarchical mergers and accretion of smaller systems driven by gravity with dark matter dominating the gravitational field. Combining X-ray and optical imaging and spectroscopy provides a powerful approach to the study of the cluster dynamics and mass assembly history. The REFLEX-DXL sample contains the most X-ray luminous galaxy clusters (L_X > 10^45 erg/s) from the REFLEX survey at z = 0.27-0.31. We present the photometric (WFI) and spectroscopic (VIMOS) data for the DXL cluster RXCJ1131.9-1955 (Abell 1300); in combination with the existing X-ray data we determine and characterise the substructure of this post-merging system. We analyse X-ray selected groups in a 30' x 30' region encompassing the cluster in order to study the mass assembly of A1300. The X-ray surface brightness map of A1300 appears disturbed and exhibits the signature of a forward shock, which is consistent with a previous analysis of radio data. Moreover, we detect a large scale-filament in which the cluster is embedded and several infalling groups. Comparison of the whirlpool-like features in the entropy pseudo-map of the intra-cluster medium with the distribution of the cluster members reveals a direct correspondence between the ICM structure and the galaxy distribution. Moreover, comparison with existing simulations allows us to better understand the dynamics of the cluster progenitors and to age date their impact. A1300 is a complex massive system in which a major merging occurred about 3 Gyr ago and additional minor merging events happen at different times via filaments, that will lead to an increase of the cluster mass of up to 60% in the next Gyr.

A Candidate Dual Active Galactic Nucleus at z=1.175

by R. Scott Barrows

Published in The Astrophysical Journal.

I am the first author on this paper. My amazing co-authors are listed in the following order: Daniel Stern, Kristin Madsen, Fiona Harrison, Roberto J. Assef, Julia M. Comerford, Michael C. Cushing, Christopher D. Fassnacht, Anthony Gonzalez, Roger Griffith, Ryan Hickox, J. Davy Kirkpatrick and David J. Lagattuta.

The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Bootes... more The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Bootes field, shows double-peaked rest-frame optical/UV emission lines, separated by 0.69" (5.5 kpc) in the spatial dimension and by 690 km s^-1 in the velocity dimension. The high excitation lines and emission line ratios indicate both systems are ionized by an AGN continuum, and the double-peaked profile resembles that of candidate dual AGN. At a redshift of z=1.175, this source is the highest redshift candidate dual AGN yet identified. However, many sources have similar emission line profiles for which other interpretations are favored. We have analyzed the substantial archival data available in this field, as well as acquired near-infrared (NIR) adaptive optics (AO) imaging and NIR slit spectroscopy. The X-ray spectrum is hard, implying a column density of several 10^23 cm^-2. Though heavily obscured, the source is also one of the brightest in the field, with an absorption-corrected 2-10 keV luminosity of ~10^45 erg s^-1. Outflows driven by an accretion disk may produce the double-peaked lines if the central engine accretes near the Eddington limit. However, we may be seeing the narrow line regions of two AGN following a galactic merger. While the AO image reveals only a single source, a second AGN would easily be obscured by the significant extinction inferred from the X-ray data. Understanding the physical processes producing the complex emission line profiles seen in CXOJ1426+35 and related sources is important for interpreting the growing population of dual AGN candidates.

Unusual double-peaked emission in the SDSS quasar J093201. 60+ 031858.7

by R. Scott Barrows

Published in New Astronomy

Co-authors: Claud H. Sandberg Lacy, Daniel Kennefick, Julia Kennefick and Marc S. Seigar

We examine spectral properties of the SDSS quasar J093201.60+031858.7, in particular the presence of strong blue peaks... more We examine spectral properties of the SDSS quasar J093201.60+031858.7, in particular the presence of strong blue peaks in the Balmer emission lines offset from the narrow lines by approximately 4200 km/s. Asymmetry in the broad central component of the Hbeta line indicates the presence of a double-peaked emitter. However, the strength and sharpness of the blue Hbeta and blue Hgamma peaks make this quasar spectrum unique amongst double-peaked emitters identified from SDSS spectra. We fit a disk model to the Hbeta line and compare this object with other unusual double-peaked quasar spectra, particularly candidate binary supermassive black holes (SMBHs). Under the binary SMBH scenario, we test the applicability of a model in which a second SMBH may produce the strong blue peak in the Balmer lines of a double-peaked emitter. If there were only one SMBH, a circular, Keplerian disk model fit would be insufficient, indicating some sort of asymmetry is required to produce the strength of the blue peak. In either case, understanding the nature of the complex line emission in this object will aid in further discrimination between a single SMBH with a complex accretion disk and the actual case of a binary SMBH.

Sum rules and interlayer infrared response of the high-Tc YBCO superconductor in an external magnetic field

by Alexander Schafgans

A.D. LaForge, W.J. Padilla, K.S. Burch, Z.Q. Li, A.A. Schafgans, Kouji Segawa, Yoichi Ando, and D.N. Basov, Phys. Rev. Lett. 101, 097008 (2008).

We present infrared magneto-optical measurements of the c-axis conductivity of YBa2Cu3Oy in both the underdoped... more We present infrared magneto-optical measurements of the c-axis conductivity of YBa2Cu3Oy in both the underdoped (y=6.67 and 6.75) and optimally doped (y=6.95) regimes. We show that modest c-axis magnetic fields radically modify the condensate formation and restore conventional BCS-like energetics. Additionally, we demonstrate the pivotal role of interplane coherence in the anomalous high-energy contribution to the superfluid density.

Electrodynamics of the vanadium oxides VO2 and V2O3

by Alexander Schafgans

M. M. Qazilbash, A. A. Schafgans, K. S. Burch, S. J. Yun, B. G. Chae, B. J. Kim, H. T. Kim, and D. N. Basov, Phys. Rev. B 77, 115121 (2008).

The optical and infrared properties of films of vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) have been... more The optical and infrared properties of films of vanadium dioxide (VO2) and vanadium sesquioxide (V2O3) have been investigated via ellipsometry and near-normal incidence reflectance measurements from far infrared to ultraviolet frequencies. Significant changes occur in the optical conductivity of both VO2 and V2O3 across the metal-insulator transitions at least up to (and possibly beyond) 6  eV. We argue that such changes in optical conductivity and electronic spectral weight over a broad frequency range are evidence of the important role of electronic correlations to the metal-insulator transitions in both of these vanadium oxides. We observe a sharp optical transition with possible final state (exciton) effects in the insulating phase of VO2. This sharp optical transition occurs between narrow a1g bands that arise from the quasi-one-dimensional chains of vanadium dimers. Electronic correlations in the metallic phases of both VO2 and V2O3 lead to reduction of the kinetic energy of the charge carriers compared to band theory values, with paramagnetic metallic V2O3 showing evidence of stronger correlations compared to rutile metallic VO2.

Optical Study of Interactions in a d-Electron Kondo Lattice with Ferromagnetism

by Alexander Schafgans

K. S. Burch, A. Schafgans, N. P. Butch, T. A. Sayles, M. B. Maple, B. C. Sales, D. Mandrus, and D. N. Basov, Phys. Rev. Lett. 95, 046401 (2005).

We report on a comprehensive optical, transport, and thermodynamic study of the Zintl compound Yb14MnSb11,... more We report on a comprehensive optical, transport, and thermodynamic study of the Zintl compound Yb14MnSb11, demonstrating that it is the first ferromagnetic Kondo lattice compound in the underscreened limit. We propose a scenario whereby the combination of Kondo and Jahn-Teller effects provides a consistent explanation of both transport and optical data.

Solvothermal synthesis of Hg1−xCdxTe nanostructures—Their structural and optical properties

by Jayakrishna Khatei

  Journal of Alloys and Compounds
Volume 509, Issue 13, 31 March 2011, Pages 4632-4635

This article describes a facile, low-cost, solution-phase approach to the large-scale preparation of Hg1−xCdxTe... more This article describes a facile, low-cost, solution-phase approach to the large-scale preparation of Hg1−xCdxTe nanostructures of different shapes such as nanorods, quantum dots, hexagonal cubes of different sizes and different compositions at a growth temperature of 180 °C using an air stable Te source by solvothermal technique. The XRD spectrum shows that the crystals are cubic in their basic structure and reveals the variation in lattice constant as a function of composition. The size and morphology of the products were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The formation of irregular shaped particles and few nano-rods in the present synthesis is attributed to the cetyl trimethylammonium bromide (CTAB). The room temperature FTIR absorption and PL studies for a compositon of x = 0.8 gives a band gap of 1.1 eV and a broad emission in NIR region (0.5–0.9 eV) with all bands attributed to surface defects.

The vibrational energy levels in acetylene. III. 12C2D2

by Alexander N. Pisarchik

We have performed the rovibrational analysis of the absorption spectrum of 12C2D2 between 5150 and 8000 cm21, recorded... more We have performed the rovibrational analysis of the absorption spectrum of 12C2D2 between 5150 and 8000 cm21, recorded by Fourier transform absorption spectroscopy, and between 12 800 and 16 600 cm21, recorded by intracavity laser absorption spectroscopy. Respectively 10 and 9 bands are reported for the first time in each range. Improved or new rovibrational parameters were obtained for 34 vibrational levels altogether. The vibrational energies we obtained, together with those reported in the literature, were taken into account to model the vibrational energy pattern in 12C2D2(X ˜ 1Sg 1). The analysis was performed in successive steps, inferring each time suitable
parameters. The 44/55, 11/33, 12/33, and 1/244 quartic order anharmonic resonances were introduced during the procedure. They altogether define vibrational clusters which are characterized by only two dynamical constants of motion, Ns5V11V21V3 and k5l41l5.