Resolution of VISION, a crystal-analyzer spectrometer

Seeger, P.A.; Daemen, Luke L.; Larese, J. Z.

doi:10.1016/j.nima.2009.03.204

Cited by 86 publications

(96 citation statements)

References 10 publications

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“…Samples were analyzed under ambient conditions at RT using EPR spectroscopy and FTIR spectroscopy, and under high vacuum at 5K using INS at the VISION beamline 23 at the Spallation Neutron Source at Oak Ridge National Laboratory.…”

Section: Methodsmentioning

confidence: 99%

Formation of environmentally persistent free radicals (EPFRs) on ZnO at room temperature: Implications for the fundamental model of EPFR generation

Patterson

DiTusa

McFerrin

et al. 2017

Chemical Physics Letters

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Environmentally persistent free radicals (EPFRs) have significant environmental and public health impacts. In this study, we demonstrate that EPFRs formed on ZnO nanoparticles provide two significant surprises. First, EPR spectroscopy shows that phenoxy radicals form readily on ZnO nanoparticles at room temperature, yielding EPR signals similar to those previously measured after 250°C exposures. Vibrational spectroscopy supports the conclusion that phenoxy-derived species chemisorb to ZnO nanoparticles under both exposure temperatures. Second, DFT calculations indicate that electrons are transferred from ZnO to the adsorbed organic (oxidizing the Zn), the opposite direction proposed by previous descriptions of EPFR formation on metal oxides.

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Section: Methodsmentioning

confidence: 99%

Formation of environmentally persistent free radicals (EPFRs) on ZnO at room temperature: Implications for the fundamental model of EPFR generation

Patterson

DiTusa

McFerrin

et al. 2017

Chemical Physics Letters

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“…The experiment was performed at the vibrational spectrometer (VISION) at SNS, ORNL [59]. The measured vDoSs in the librational band are shown in Fig.…”

Section: H Y S I C a L R E V I E W L E T T E R S Week Ending 4 Decembmentioning

confidence: 99%

Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

et al. 2015

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The boson peak in deeply cooled water confined in nanopores is studied to examine the liquid-liquid transition (LLT). Below ∼180 K, the boson peaks at pressures P higher than ∼3.5 kbar are evidently distinct from those at low pressures by higher mean frequencies and lower heights. Moreover, the higher-P boson peaks can be rescaled to a master curve while the lower-P boson peaks can be rescaled to a different one. These phenomena agree with the existence of two liquid phases with different densities and local structures and the associated LLT in the measured (P, T) region. In addition, the P dependence of the librational band also agrees with the above conclusion. DOI: 10.1103/PhysRevLett.115.235701 PACS numbers: 64.70.Ja, 25.40.Fq, 63.50.-x Water is a continuing source of fascination to scientists because of its abnormal behavior at low temperatures T. Upon cooling, its thermodynamic properties, such as density, isobaric heat capacity, and isobaric thermal expansivity, deviate from those of simple liquids significantly [1][2][3][4]. In addition, glassy water, also called amorphous ice, exhibits polyamorphism. Experiments show that two kinds of amorphous ice, low-density amorphous ice (LDA) and high-density amorphous ice (HDA), exist at very low temperatures [5][6][7]. These two phases can transform to each other through a first-order-like transition [7,8]. To account for these mysterious phenomena, a "liquid-liquid critical point (LLCP)" scenario, which assumes a first-order low-density liquid (LDL) to high-density liquid (HDL) phase transition in the deeply cooled region of liquid water, has been proposed [9]. Therefore, experimental tests on the existence of the LDL and the HDL and the associated liquid-liquid transition (LLT) are important for understanding water. Nevertheless, such measurements are practically difficult due to the rapid crystallization of bulk water below the homogeneous nucleation temperature (235 K at 1 atm). To overcome this barrier and enter the deeply cooled region of water, different systems, including aqueous solutions [10][11][12][13][14], microsized water droplets [15], and confined water systems [16][17][18][19], have been prepared and studied. Particularly, when confined in a nanoporous silica matrix, MCM-41, with a 15-Å pore diameter, water can be kept in the liquid state at least down to 130 K [20,21]. Thus, the MCM-41-confined water system provides a chance to explore the hypothetical LLT.Recently, we observed a likely LLT in heavy water confined in MCM-41 by a density measurement. The associated phase diagram is shown in Fig. 1(a) [22]. However, the relevant measurements on the dynamic properties are still lacking. In fact, various dynamic properties, including the structural relaxation [10,16], the stretching vibration [10,11], the mean square displacement [23], etc., have been measured to study the phase behaviors of aqueous solutions or confined water. Examinations of FIG. 1 (color online). (a) Phase diagram of deeply cooled confined heavy water [22]. The inset shows th...

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“…However, there is basic difference with respect to ISIS, namely the intrinsic time structure of the ESS primary neutron beam and the presence of the time shaping chopper. Thus, we decided to use a different formula that was reported in a recent paper by Seegers et al [8] to evaluate the expected performances of the VISION spectrometer at SNS. With reference to Fig.…”

Section: Expected Resolving Powermentioning

confidence: 99%

“…[8], apart from σ RA 2 that in our case was adapted to a vertical crystal analyser size of 10 cm. It turns out that only two terms in Eq.…”

Section: Expected Resolving Powermentioning

confidence: 99%

VSI@ESS: Case study for a vibrational spectroscopy instrument at the european spallation source

Zoppi

Fedrigo

Celli

et al. 2015

EPJ Web of Conferences

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Abstract. Neutron Vibrational Spectroscopy is a well-established experimental technique where elementary excitations at relatively high frequency are detected via inelastic neutron scattering. This technique attracts a high interest in a large fraction of the scientific community in the fields of chemistry, materials science, physics, and biology, since one of its main applications exploits the large incoherent scattering cross section of the proton with respect to all the other elements, whose dynamics can be spectroscopically detected, even if dissolved in very low concentration in materials composed of much heavier atoms. We have proposed a feasibility study for a Vibrational Spectroscopy Instrument (VSI) at the European Spallation Source ESS. Here, we will summarize the preliminary design calculations and the corresponding McStas simulation results for a possible ToF, Inverted Geometry, VSI beamline. MotivationsVibrational Spectroscopy (VS) is an experimental technique that is widely used in the innumerable research laboratories worldwide. When the electromagnetic (EM) radiation is used to probe sample properties, this technique is generally much better known as Infrared Absorption (IA) spectroscopy (a first order interaction process between photons and sample), or as Raman Scattering (RS) spectroscopy (a second order interaction process between photons and sample). However, when matter becomes opaque to the EM radiation or, more generally, the inhomogeneity of the material prevents a deep penetration of the photons in the sample, then the drastic reduction of the effective scattering volume makes the optical methods rather inefficient to probe the bulk properties of the sample and other probes, alternative to EM radiation, should be considered.Thermal neutrons actually possess the aforementioned characteristics. Their penetration depth in dense matter is roughly independent of the atomic composition and, apart from a few selected and well-defined atomic species, it can easily reach several centimetres below surface, in the bulk volume of the sample [1]. In addition, as neutrons interact directly with nuclei, their scattering properties are not subject to selection rules, which affect IA spectroscopy (electric dipole transitions) and RS spectroscopy (electric polarizability transitions).Thermal neutron spectroscopic techniques, however, cannot be considered as the panacea for every difficult scientific problem. As a matter of fact, given the high cost of neutrons production and instrumentation, their use must be consequently limited to very special problems whose solution cannot be faced by more standard laboratory techniques. Nonetheless, an increasing number of research a Corresponding author: marco.zoppi@isc.cnr.it activities needs neutrons as the unique probe which is able to give a quantitative answer to well selected problems concerning the atomic structure and dynamics in a large class of relevant materials. For this reasons, the European scientific community is operating to build in the nearfuture a ...

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Resolution of VISION, a crystal-analyzer spectrometer

Cited by 86 publications

References 10 publications

Formation of environmentally persistent free radicals (EPFRs) on ZnO at room temperature: Implications for the fundamental model of EPFR generation

Formation of environmentally persistent free radicals (EPFRs) on ZnO at room temperature: Implications for the fundamental model of EPFR generation

Pressure Effect on the Boson Peak in Deeply Cooled Confined Water: Evidence of a Liquid-Liquid Transition

VSI@ESS: Case study for a vibrational spectroscopy instrument at the european spallation source

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