Search results for "absorption spectroscopy"
showing 10 items of 828 documents
Potentials for modeling cold collisions between Na (3S) and Rb (5S) atoms
2005
The experimental characterization of the electronic states correlated to the asymptote of ground state Na (3S) and Rb (5S) atoms was expanded by spectroscopic data on $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ state levels using a high resolution Fourier transform spectroscopy technique. The hyperfine splitting of the $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ state levels was partially resolved and analyzed for both $\mathrm{Na}\phantom{\rule{0.2em}{0ex}}^{85}\mathrm{Rb}$ and $\mathrm{Na}\phantom{\rule{0.2em}{0ex}}^{87}\mathrm{Rb}$ isotopomers. Transitions to high lying levels of the $a\phantom{\rule{0.2em}{0ex}}^{3}\ensuremath{\Sigma}^{+}$ and $X\phantom{\rul…
The High Resolution Infrared Spectrum of CH3D in the Region 900–1700 cm−1
1997
The high resolution absorption spectrum of CH(sub 3)D in the region of 900-1700 cm(sup -1) has been revisited on the basis of new long path experimental data recorded with the Fourier transform spectrometer at Kitt Peak. A theoretical model used previously for spherical rotors has been adapted for polyatomic molecules in order to analyze the vibrational polyads of CH(sub 3)D simultaneously.
Chandra Observation of the Dipping Source XB 1254-690
2006
We present the results of a 53 ks long Chandra observation of the dipping source XB 1254--690. During the observation neither bursts or dips were observed. From the zero-order image we estimated the precise X-ray coordinates of the source with a 90% uncertainty of 0.6\arcsec. Since the lightcurve did not show any significant variability, we extracted the spectrum corresponding to the whole observation. We confirmed the presence of the \ion{Fe}{xxvi} K$_\alpha$ absorption lines with a larger accuracy with respect to the previous XMM EPIC pn observation. Assuming that the line width were due to a bulk motion or a turbulence associated to the coronal activity, we estimate that the lines were p…
Photoionization of Oriented Systems and Circular Dichroism
1996
Circular dichroism (CD) spectroscopy is a modification of normal absorption spectroscopy using circularly polarized light instead of unpolarized light for determining the difference in the absorption coefficients for right and left circularly polarized light, respectively, in optically active samples. Thus, there is nothing mysterious about CD spectroscopy. However, relative to most other spectroscopic techniques there seems to be a large psychological barrier in its application and at least physicists often regard CD, and optical activity in general, as a rather obscure technique without any useful application. There are some understandable reasons for this attitude, manifesting themselves…
Controlled type-I–type-II transition in GaAs/AlAs/AlxGa1−xAs double-barrier quantum wells
1997
We show that the insertion of extremely narrow AlAs layers in double-barrier GaAs/AlAs/${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As quantum wells results in a variety of electronic configurations, thus providing a powerful tool for tailoring the electronic transitions in GaAs heterostructures. In particular, the transition from type-I to type-II recombination is shown to occur in correspondence with variations by a single monolayer in the thickness of the AlAs and/or GaAs layers. Drastic changes in the recombination lifetimes are correspondingly observed; at the same time, the photoluminescence efficiency is found to be almost independent of the type-I-…
Unraveling exciton dynamics in amorphous silicon dioxide: Interpretation of the optical features from 8 to 11 eV.
2011
Physical review / B 83, 174201 (2011). doi:10.1103/PhysRevB.83.174201
Local structure aroundEr3+inSiO2−HfO2glassy waveguides using EXAFS
2007
${\mathrm{Er}}^{3+}$-doped $\mathrm{Si}{\mathrm{O}}_{2}\text{\ensuremath{-}}\mathrm{Hf}{\mathrm{O}}_{2}$ glassy waveguides with $\mathrm{Hf}{\mathrm{O}}_{2}$ concentrations ranging from $10\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}50\phantom{\rule{0.3em}{0ex}}\mathrm{mol}\phantom{\rule{0.2em}{0ex}}%$ were prepared using the sol-gel route and deposited on $v\text{\ensuremath{-}}\mathrm{Si}{\mathrm{O}}_{2}$ substrates using the dip-coating technique. The local environment around ${\mathrm{Er}}^{3+}$ ions was determined from Er ${L}_{3}$-edge extended x-ray-absorption fine-structure (EXAFS) measurements. The first coordination shell around ${\mathrm{Er}}^{3+}$ ions is comp…
Line strengths of the ν2 + ν3 and ν3 − ν2 bands of methane (12CH4)
1992
Abstract The individual linestrengths of two related bands of 12 CH 4 , ν 2 + ν 3 near 4545 cm −1 and ν 3 − ν 2 near 1484 cm −1 , were measured with accuracies of 3% and 5%, respectively. In the analysis, an eight-term expansion of the dipole moment through second order was required to fit the strengths of transitions up to J ′ = 10 in ν 2 + ν 3 and J ′ = 12 in ν 3 − ν 2 and to explain the considerable perturbations observed. Application of this model reduced the rms deviations from 68% (zero-order) to 6.3% with the 248 selected lines of ν 2 + ν 2 and from 37% to 5.8% with 186 lines of ν 3 − ν 2 . The integrated bandstrengths for the two bands, respectively, are 1.84(5) and 0.0085(4) cm −2 …
Solvation of triplet Rydberg states of molecular hydrogen in superfluid helium
2004
We report ab initio interaction potentials, transition dipole moments, and radiative lifetimes for the four lowest triplet states of ${\mathrm{H}}_{2}:$ $b$ ${}^{3}{\ensuremath{\Sigma}}_{u}^{+},$ $c$ ${}^{3}{\ensuremath{\Pi}}_{u},$ $a$ ${}^{3}{\ensuremath{\Sigma}}_{g}^{+},$ and $e$ ${}^{3}{\ensuremath{\Sigma}}_{u}^{+},$ and their response to the perturbation due to approaching ground state He atom. Hybrid density functional\char21{}quantum Monte Carlo calculations employing the ab initio interaction potentials are then used for calculating the liquid structure around the molecular excimers in bulk superfluid ${}^{4}\mathrm{He}.$ Calculations demonstrate a wide variety of possible solvation …
On the soft excess in the x-ray spectrum of circinus X-1: Revisitation of the distance to circinus X-1
2005
We report on a 300 ks BeppoSAX (0.12-200 keV) observation of Circinus X-1 (Cir X-1) at phases between 0.62 and 0.84 and on a 90 ks BeppoSAX observation of Cir X-1 at phases 0.11-0.16. Using the canonical model adopted until now to fit the energy spectrum of this source, large residuals appear below 1 keV. These are well fitted using an equivalent hydrogen column of 0.66¿1022 cm-2, adding absorption edges of O VII, O VIII, and Ne IX in the spectra extracted from the observation at phases 0.62-0.84 and adding absorption edges of O VII, O VIII, Mg XI, and Mg XII and absorption lines of O VIII and Mg XII in the spectra extracted from the observation at phases 0.11-0.16. During the observation a…