Elementary excitations in condensed oxygen (α,β,γ, liquid) by high-resolution Raman scattering

Kreutz, Jörg; Jodl, H. J.

doi:10.1103/physrevb.68.214303

Cited by 12 publications

(12 citation statements)

References 46 publications

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“…Figure shows the oxygen vibron as a function of concentration at two different temperatures: at T = 14 K (Figure a) and at T = 42 K (Figure b). The true bandwidth of vibrons in pure oxygen is very narrow (<0.1 cm -1 , high-resolution Raman spectra of pure α-O 2 and γ-O 2 are plotted with broken lines in Figure ), whereas the resolution in our spectra of the mixed systems was ∼2 cm -1 . Therefore, the spectral features at higher temperatures (Figure b) must contain at least two contributions due to different surroundings (N 2 /O 2 ) or due to the doublet in pure γ-O 2 (1552 and 1553 cm -1 , intensity ratio 3:1).…”

Section: Resultsmentioning

confidence: 86%

“…The vibron spectrum of (N 2 ) 0.78 (O 2 ) 0.22 in Figure contains two bands at lower temperatures ( T < 39 K) and only one band at higher temperatures ( T > 39 K). The band at 1552.5 cm -1 is known from pure solid α-O 2 and β-O 2 , the band at 1555.5 cm -1 is known from matrix-isolated O 2 in α-N 2 . Therefore, the spectra at T < 32.5 K we assign to α*-O 2 (or β*-O 2 ) and α*-N 2 .…”

Section: Resultsmentioning

confidence: 99%

“…In the first step we discuss the low-temperature spectra (Figure a).

7 Raman spectra of O 2 internal vibrations: (a) for two different concentrations at the lowest temperature; (b) for three different concentrations at 42 K. High-resolution Raman spectra of pure α-O 2 and γ-O 2 are added for comparison (broken line at bottom) …”

Section: Resultsmentioning

confidence: 99%

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Raman Investigation of the N₂−O₂ Binary System as a Function of Pressure and Temperature

et al. 2004

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We produced mixtures of N2-O2 with different concentrations and performed low-temperature Raman studies at ambient and high pressures. From spectra in vibron and phonon regions, we determined band frequency, bandwidth, and band intensity as a function of temperature, pressure, and concentration. We determined the vibron Raman cross-sections and deduced the true concentrations of mixtures from vibron Raman band intensities. These concentrations were different from those determined from partial gas pressure of the initial gaseous mixtures. From fingerprints in Raman spectra, such as jumps in band frequencies or additional band splitting, we were able to prove phase transitions and propose a preliminary T-x phase diagram. We compared this diagram with two reported in the literature from structural analysis. Comparing all three variants of the T-x phase diagrams we found several discrepancies and inconsistencies, which we associate with different solid sample production techniques. Since we could prove that our samples were in thermodynamic equilibrium, we are convinced that we improved the known phase diagram substantially. From Raman band intensities of the O2 vibrations in different phases of N2 and O2, we were able to determine quantitatively the solubility of O2 in N2. Preliminary Raman studies of 2% and 7% O2 in N2 at high pressure and low temperatures showed that a larger amount of O2 can be dissolved in N2 than at ambient pressure. At the critical pressure (p approximately 15 GPa) we found from Raman spectra that O2 is demixed from 7% O2 in N2 to form epsilon-O2. This was previously called a "new phase" in the literature and not understood up to now. Finally, from band frequencies we determined the environmental shift of oxygen molecules in the mixture which is related to the intermolecular potential U(N2-O2) between different types of molecules.

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Section: Resultsmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

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Raman Investigation of the N₂−O₂ Binary System as a Function of Pressure and Temperature

et al. 2004

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“…For one, 16 O has a neutron absorption cross-section five times smaller than that of 2 H. In addition to phonons, solid oxygen (s-O 2 ) in its low temperature phases has strong magnetic interactions which could be harnessed for UCN production [18]. These magnetic excitations have been widely studied using Raman scattering [19,20] as well as neutron scattering [21][22][23]. It has been shown that the low temperature phases possess very different dynamics that often entangle translational, librational, and spin excitations through the orientation-dependent couplings between the diatomic oxygen molecules on the solid lattice sites.…”

Section: Introductionmentioning

confidence: 99%

Ultracold-neutron production in a pulsed-neutron beam line

et al. 2010

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We present the results of an Ultracold neutron (UCN) production experiment in a pulsed neutron beam line at the Los Alamos Neutron Scattering Center. The experimental apparatus allows for a comprehensive set of measurements of UCN production as a function of target temperature, incident neutron energy, target volume, and applied magnetic field. However, the low counting statistics of the UCN signal expected can be overwhelmed by the large background associated with the scattering of the primary cold neutron flux that is required for UCN production. We have developed a background subtraction technique that takes advantage of the very different time-of-flight profiles between the UCN and the cold neutrons, in the pulsed beam. Using the unique timing structure, we can reliably extract the UCN signal. Solid ortho-D2 is used to calibrate UCN transmission through the apparatus, which is designed primarily for studies of UCN production in solid O2. In addition to setting the overall detection efficiency in the apparatus, UCN production data using solid D2 suggest that the UCN upscattering cross-section is smaller than previous estimates, indicating the deficiency of the incoherent approximation widely used to estimate inelastic cross-sections in the thermal and cold regimes.

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“…We have identified an additional phenomenon of ␣-O 2 that is intimately connected with its magnetism: Twolibron excitations have been observed in our zero-pressure Raman measurements. 32 These we explained as originating with magnetic coupling of two molecules in the primitive cell performing librations. In our recent low-pressure Raman study 16 on ␣ oxygen we found that due to an enhancement of the spin coupling mechanism, the intensities of two-libron excitations increase by a factor of about 5 as one applies pressure from 0 to 1.25 GPa.…”

Section: Magnetism In the ␣ And ␦ Phasesmentioning

confidence: 94%

Low-temperature phases of solid oxygen at pressures up to8GPadetermined by Raman and infrared spectroscopy

2005

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We report studies of vibron, libron, and combined two-libron excitations of solid oxygen in the pressure range up to 8 GPa using Raman scattering and infrared absorption at low temperatures. We took care to ensure that our samples have been close to thermodynamic equilibrium, as confirmed by additional measurements. On the basis of these results we present a revised phase diagram of thermodynamically stable oxygen. There the ␣ phase exists up to temperatures of the ␤ phase and up to a pressure of about 6 GPa, where a clear first-order transition to the ␦ phase occurs. Our spectroscopically determined phase diagram is in accordance with the structurally determined one by Gorelli et al. ͓Phys. Rev. B 65, 172106 ͑2002͔͒. Inconsistencies with other reported phase diagrams can be attributed to the fact that those samples were not at equilibrium. Furthermore, we provide an indirect proof, using Raman spectroscopy, of the antiferromagnetic order of ␦-O 2 . The present Raman and infrared investigations together with spectroscopic, x-ray, and neutron data provide a consistent picture of oxygen in the p-T range investigated here.

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Elementary excitations in condensed oxygen (α,β,γ, liquid) by high-resolution Raman scattering

Cited by 12 publications

References 46 publications

Raman Investigation of the N₂−O₂ Binary System as a Function of Pressure and Temperature

Raman Investigation of the N₂−O₂ Binary System as a Function of Pressure and Temperature

Ultracold-neutron production in a pulsed-neutron beam line

Low-temperature phases of solid oxygen at pressures up to8GPadetermined by Raman and infrared spectroscopy

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Elementary excitations in condensed oxygen (α,β,γ, liquid) by high-resolution Raman scattering

Cited by 12 publications

References 46 publications

Raman Investigation of the N2−O2 Binary System as a Function of Pressure and Temperature

Raman Investigation of the N2−O2 Binary System as a Function of Pressure and Temperature

Ultracold-neutron production in a pulsed-neutron beam line

Low-temperature phases of solid oxygen at pressures up to8GPadetermined by Raman and infrared spectroscopy

Contact Info

Product

Resources

About

Raman Investigation of the N₂−O₂ Binary System as a Function of Pressure and Temperature

Raman Investigation of the N₂−O₂ Binary System as a Function of Pressure and Temperature