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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Isotropic rotation vs. shear relaxation in supercooled liquids with globular cage molecules

The temperature dependence of the rotational dynamics of P{sub 4}Se{sub 3} molecules in the glass-forming molecular liquid P{sub 5}Se{sub 3} is studied using two-dimensional {sup 31}P nuclear magnetic resonance spectroscopy. Unlike typical molecular glass-forming liquids, the constituent molecules in the P{sub 5}Se{sub 3} liquid perform rapid isotropic rotation without significant translational diffusion in the supercooled regime and this rotational process shows a decoupling in time scale from shear relaxation by nearly six orders of magnitude at the glass transition. This dynamical behavior of liquid-like rotation and localized translation appears to be universal to glass-forming liquids with high-symmetry globular molecules that are characterized by an underlying thermodynamically stable plastic crystal phase.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Interactions of gas molecules with monolayer MoSe{sub 2}: A first principle study

We present a first principle study of interaction of toxic gas molecules (NO, NO{sub 2} and SO{sub 2}) with monolayer MoSe{sub 2}. The predicted order of sensitivity of gas molecule is NO{sub 2} > SO{sub 2} > NO. Adsorbed molecules strongly influence the electronic behaviour of monolayer MoSe{sub 2} by inducing impurity levels in the vicinity of Fermi energy. NO and SO{sub 2} is found to induce p-type doping effect while semiconductor to metallic transitions occur on NO{sub 2} adsorption. Our findings may guide the experimentalist for fabricating sensor devices based on MoSe{sub 2} monolayer.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Raman scattering mediated by neighboring molecules

Raman scattering is most commonly associated with a change in vibrational state within individual molecules, the corresponding frequency shift in the scattered light affording a key way of identifying material structures. In theories where both matter and light are treated quantum mechanically, the fundamental scattering process is represented as the concurrent annihilation of a photon from one radiation mode and creation of another in a different mode. Developing this quantum electrodynamical formulation, the focus of the present work is on the spectroscopic consequences of electrodynamic coupling between neighboring molecules or other kinds of optical center. To encompass these nanoscale interactions, through which the molecular states evolve under the dual influence of the input light and local fields, this work identifies and determines two major mechanisms for each of which different selection rules apply. The constituent optical centers are considered to be chemically different and held in a fixed orientation with respect to each other, either as two components of a larger molecule or a molecular assembly that can undergo free rotation in a fluid medium or as parts of a larger, solid material. The two centers are considered to be separated beyond wavefunction overlap but close enough together to fall within an optical near-field limit, which leads to high inverse power dependences on their local separation. In this investigation, individual centers undergo a Stokes transition, whilst each neighbor of a different species remains in its original electronic and vibrational state. Analogous principles are applicable for the anti-Stokes case. The analysis concludes by considering the experimental consequences of applying this spectroscopic interpretation to fluid media; explicitly, the selection rules and the impact of pressure on the radiant intensity of this process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

BODIPY star-shaped molecules as solid state colour converters for visible light communications

In this paper, we study a family of solid-state, organic semiconductors for visible light communications. The star-shaped molecules have a boron-dipyrromethene (BODIPY) core with a range of side arm lengths which control the photophysical properties. The molecules emit red light with photoluminescence quantum yields ranging from 22% to 56%. Thin films of the most promising BODIPY molecules were used as a red colour converter for visible light communications. The film enabled colour conversion with a modulation bandwidth of 73 MHz, which is 16 times higher than that of a typical phosphor used in LED lighting systems. A data rate of 370 Mbit/s was demonstrated using On-Off keying modulation in a free space link with a distance of ∼15 cm.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Formation of blade and slot die coated small molecule multilayers for OLED applications studied theoretically and by XPS depth profiling

Slot die coaters especially designed for low material consumption and doctor blades were used to process small molecule solutions for organic light-emitting diodes (OLEDs). Optimum process parameters were developed for the large-scale coating techniques to generate stable single and multiple layers only a few nanometers thick. Achieving a multilayer architecture for solution-processed OLEDs is the most challenging step. X-ray photoelectron spectroscopy sputter depth profiling was performed to determine defined interfaces between coated organic layers. Commercially available small molecules NPB (N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4,4’-diamine) and BAlq (Bis(8-hdroxy-2methylquinoline)-(4-phenylphenoxy)aluminum), originally developed for vacuum deposition, were used as hole, respectively electron transport material. Defined double-layers were processed with both scalable coating methods using the orthogonal solvent approach. The use of non-orthogonal solvents resulted in complete intermixing of the material. The results are explained by calculations of solubilities and simulating drying and diffusion kinetics of the small molecule solutions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Spin-free formulation of the multireference driven similarity renormalization group: A benchmark study of first-row diatomic molecules and spin-crossover energetics

We report a spin-free formulation of the multireference (MR) driven similarity renormalization group (DSRG) based on the ensemble normal ordering of Mukherjee and Kutzelnigg (1997). This ensemble averages over all microstates of a given total spin quantum number, and therefore, it is invariant with respect to SU(2) transformations. As such, all equations may be reformulated in terms of spin-free quantities and they closely resemble those of spin-adapted closed-shell coupled cluster (CC) theory. The current implementation is used to assess the accuracy of various truncated MR-DSRG methods (perturbation theory up to third order and iterative methods with single and double excitations) in computing the constants of 33 first-row diatomic molecules. The accuracy trends for these first-row diatomics are consistent with our previous benchmark on a small subset of closed-shell diatomic molecules. We then present the first MR-DSRG application on transition-metal complexes by computing the spin splittings of the [Fe(H 2 O) 6 ] 2+ and [Fe(NH 3 ) 6 ] 2+ molecules. A focal point analysis (FPA) shows that third-order perturbative corrections are essential to achieve reasonably converged energetics. The FPA based on the linearized MR-DSRG theory with one- and two-body operators and up to a quintuple- ζ basis set predicts the spin splittings of [Fe(H 2 O) 6 ] 2+ and [Fe(NH 3 ) 6 ] 2+ to be –35.7 and –17.1 kcal mol –1 , respectively, showing good agreement with the results of local CC theory with singles, doubles, and perturbative triples.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

Interstitial BiO molecule as a broadband IR luminescence centre in bismuth-doped silica glass

Experimental data on absorption and luminescence in optical fibres with a Bi : SiO{sub 2} glass core are compared to experimentally determined and calculated spectroscopic properties of the BiO molecule. The results suggest that the IR luminescence of Bi : SiO{sub 2} glass is due to interstitial BiO molecules. This assumption is supported by quantum-chemical simulation results for a BiO molecule in a ring interstice of the silica glass network.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Investigation of interaction of albumin molecules with diamond nanoparticles in aqueous solutions by dynamic light scattering

The method of dynamic light scattering has been used to study the interaction of albumin molecules with diamond nanoparticles in aqueous solutions. It is shown that due to adsorption of albumin on diamond nanoparticles, larger size particles are formed. We have obtained the concentration dependences of the average hydrodynamic radius of these particles. It is found that the carboxylation of the surface of diamond nanoparticles and their pre-coating by albumin leads to a decrease in the adsorption of protein molecules on the surface of nanoparticles and to a decrease in their average hydrodynamic radius. We have also shown that in the range of concentrations of diamond nanoparticles 2-10 {mu}g mL{sup -1}, their interaction with albumin molecules at different pH has a different character.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Luminescence characteristics of Xe{sub 2}Cl excimer molecules under pumping the dense Xe-CCl{sub 4} gas mixtures with a pulsed electron beam

Temporal and spectral characteristics of the luminescence of dense Xe-CCl{sub 4} gas mixtures of different composition, excited by a 5-ns pulsed electron beam, were measured. The energy of the electrons amounted to 150 keV and the electron beam current pulse amplitude was 5 A. The gas mixtures were used containing Xe (38-700 Torr) and CCl{sub 4} (0.03-0.3 Torr). The studies were performed within the wavelength range 200-1200 nm using a MAYA-2000Pro diffraction grating spectrometer and a RIGOL DS 5022 ME fast digital oscilloscope. The luminescence lifetimes of the excimer molecules XeCl* (band with {lambda}{sub max} = 308 nm) and Xe{sub 2}Cl* (band with {lambda}{sub max} = 486 nm) were measured, as well as the constants of quenching by the components of the gas mixture for Xe{sub 2}Cl* molecules. A model of plasma-chemical processes for dense Xe-CCl{sub 4} gas mixtures with a very low content of the CCl{sub 4} donor is proposed. It is shown that in such 'poor' mixtures Xe{sub 2}Cl* molecules are mainly produced as a result of recombination of the Xe{sub 2}{sup +} and Cl{sup -} ions. (active media)

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Spontaneous emission of a chiral molecule near a cluster of two chiral spherical particles

We have obtained and investigated analytical expressions for the radiative spontaneous decay rate of a chiral (optically active) molecule located near a cluster of two identical chiral (biisotropic) spherical particles. It is found that the composition of the particles, their location and size have a significant effect on the spontaneous emission of chiral molecules. In particular, it is shown that in the case of nanoparticles of chiral metamaterials, the radiative spontaneous decay rate for the 'right-' and 'left-handed' enantiomers of chiral molecules located in the gap of the cluster are significantly different. (metamaterials)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Experimental results on the dissociation of molecular iodine in the presence of singlet oxygen molecules

The experimental results on the dissociation of iodine molecules in the presence of single oxygen molecules under a widerange variation of the oxygen–iodine composition are presented. The rate constants are determined as 4.3 × 10{sup -17} cm{sup 3} s{sup -1} for the reaction O{sub 2}({sup 1}Δ) + O{sub 2}({sup 1}Δ) → O{sub 2}({sup 1}Σ) + O{sub 2}({sup 3}Σ) (reaction 1), 2.8 × 10{sup -13} cm{sup 3} s{sup -1} for the reaction O{sub 2}({sup 1}Δ) + I({sup 2}P{sub 1/2}) → O{sub 2}({sup 1}Σ) + I({sup 2}P{sub 3/2}) (4) and 8.3 × 10{sup -11} cm{sup 3} s{sup -1} for the reaction O{sub 2}({sup 1}Σ) + I{sub 2} → O{sub 2}({sup 3}Σ) + 2I (2). The analysis of the experimental results shows that for different compositions of the active medium of the oxygen–iodine laser the iodine dissociation occurs via the chain of reactions 1, 2, O{sub 2}({sup 1}Δ) + I({sup 2}P{sub 3/2}) → O{sub 2}({sup 3}Σ) + I({sup 2}P{sub 1/2}), 4 and in the cascade process I{sub 2} + I({sup 2}P{sub 1/2}) → I{sub 2}(u) + I({sup 2}P{sub 3/2}), I{sub 2}(u) + O{sub 2}({sup 1}Δ) → 2I + O{sub 2}({sup 3}Σ). For typical active medium compositions of the supersonic chemical oxygen–iodine laser, the contributions of each of the mechanisms to the dissociation are comparable. The experiments carried out did not reveal any contribution from the vibrationally excited oxygen molecules to the iodine dissociation. Thus, the performed experiments and the conclusions drawn from them completely confirm the mechanism of iodine dissociation, proposed earlier. (active media)

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2011

CIRCUMSTELLAR ION-MOLECULE CHEMISTRY: OBSERVATIONS OF HCO{sup +} IN THE ENVELOPES OF O-RICH STARS AND IRC+10216

Millimeter-wave observations of HCO{sup +} have been conducted toward oxygen-rich circumstellar envelopes, as well as IRC+10216, using the facilities of the Arizona Radio Observatory (ARO). The J = 1 {yields} 0 and 2 {yields} 1 transitions of this molecule were measured with the ARO 12 m antenna, while the J = 3 {yields} 2 and 4 {yields} 3 lines were observed using the ARO Sub-Millimeter Telescope. HCO{sup +} was detected toward the supergiant NML Cyg and the asymptotic giant branch (AGB) stars IK Tau, TX Cam, and W Hya in at least two transitions. The J = 2 {yields} 1 and 3 {yields} 2 lines of this ion were also detected toward IRC+10216, confirming the identification of HCO{sup +} in this object. The line profiles measured for HCO{sup +} toward NML Cyg consist of red- and blueshifted components, suggesting a non-spherical shell. Based on a radiative transfer analysis, the abundances in the O-rich envelopes were f(HCO{sup +}/H{sub 2}) {approx} 0.15-1.3 Multiplication-Sign 10{sup -7}, with the AGB stars typically exhibiting the higher values. In IRC+10216, f(HCO{sup +}/H{sub 2}) {approx} 4.1 Multiplication-Sign 10{sup -9}, lower than the O-rich counterparts. The abundances of HCO{sup +} were also found to peak at considerable distances from the star, indicative of an outer envelope molecule. Comparison with H{sub 2}O and CO, the main precursor species, suggests that HCO{sup +} is more prevalent in envelopes that have substantial water, but CO also plays a role in its formation. The abundance of HCO{sup +} appears to increase inversely with mass-loss rate, provided the rate is >10{sup -6} M{sub Sun} yr{sup -1}. The common appearance of HCO{sup +} in circumstellar gas indicates that, at some level, ion-molecule reactions influence the chemistry of evolved stellar envelopes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

ELECTRON IRRADIATION OF CARBON DISULFIDE-OXYGEN ICES: TOWARD THE FORMATION OF SULFUR-BEARING MOLECULES IN INTERSTELLAR ICES

The formation of sulfur-bearing molecules in interstellar ices was investigated during the irradiation of carbon disulfide (CS{sub 2})-oxygen (O{sub 2}) ices with energetic electrons at 12 K. The irradiation-induced chemical processing of these ices was monitored online and in situ via Fourier transform infrared spectroscopy to probe the newly formed products quantitatively. The sulfur-bearing molecules produced during the irradiation were sulfur dioxide (SO{sub 2}), sulfur trioxide (SO{sub 3}), and carbonyl sulfide (OCS). Formations of carbon dioxide (CO{sub 2}), carbon monoxide (CO), and ozone (O{sub 3}) were observed as well. To fit the temporal evolution of the newly formed products and to elucidate the underlying reaction pathways, kinetic reaction schemes were developed and numerical sets of rate constants were derived. Our studies suggest that carbon disulfide (CS{sub 2}) can be easily transformed to carbonyl sulfide (OCS) via reactions with suprathermal atomic oxygen (O), which can be released from oxygen-containing precursors such as water (H{sub 2}O), carbon dioxide (CO{sub 2}), and/or methanol (CH{sub 3}OH) upon interaction with ionizing radiation. This investigation corroborates that carbonyl sulfide (OCS) and sulfur dioxide (SO{sub 2}) are the dominant sulfur-bearing molecules in interstellar ices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

SURVIVAL OF INTERSTELLAR MOLECULES TO PRESTELLAR DENSE CORE COLLAPSE AND EARLY PHASES OF DISK FORMATION

An outstanding question of astrobiology is the link between the chemical composition of planets, comets, and other solar system bodies and the molecules formed in the interstellar medium. Understanding the chemical and physical evolution of the matter leading to the formation of protoplanetary disks is an important step for this. We provide some new clues to this long-standing problem using three-dimensional chemical simulations of the early phases of disk formation: we interfaced the full gas-grain chemical model Nautilus with the radiation-magnetohydrodynamic model RAMSES, for different configurations and intensities of the magnetic field. Our results show that the chemical content (gas and ices) is globally conserved during the collapsing process, from the parent molecular cloud to the young disk surrounding the first Larson core. A qualitative comparison with cometary composition suggests that comets are constituted of different phases, some molecules being direct tracers of interstellar chemistry, while others, including complex molecules, seem to have been formed in disks, where higher densities and temperatures allow for an active grain surface chemistry. The latter phase, and its connection with the formation of the first Larson core, remains to be modeled.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

The census of complex organic molecules in the solar-type protostar IRAS16293-2422

Complex organic molecules (COMs) are considered to be crucial molecules, since they are connected with organic chemistry, at the basis of terrestrial life. More pragmatically, they are molecules which in principle are difficult to synthesize in harsh interstellar environments and, therefore, are a crucial test for astrochemical models. Current models assume that several COMs are synthesized on lukewarm grain surfaces (≳30-40 K) and released in the gas phase at dust temperatures of ≳100 K. However, recent detections of COMs in ≲20 K gas demonstrate that we still need important pieces to complete the puzzle of COMs formation. Here, we present a complete census of the oxygen- and nitrogen-bearing COMs, previously detected in different Interstellar Medium (ISM) regions, toward the solar-type protostar IRAS16293-2422. The census was obtained from the millimeter-submillimeter unbiased spectral survey TIMASSS. Of the 29 COMs searched for, 6 were detected: methyl cyanide, ketene, acetaldehyde, formamide, dimethyl ether, and methyl formate. Multifrequency analysis of the last five COMs provides clear evidence that they are present in the cold (≲30 K) envelope of IRAS16293-2422, with abundances of 0.03-2 × 10{sup –10}. Our data do not allow us to support the hypothesis that the COMs abundance increases with increasing dust temperature in the cold envelope, as expected if COMs were predominately formed on lukewarm grain surfaces. Finally, when also considering other ISM sources, we find a strong correlation over five orders of magnitude between methyl formate and dimethyl ether, and methyl formate and formamide abundances, which may point to a link between these two couples of species in cold and warm gas.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A THEORETICAL STUDY ON THE VIBRATIONAL SPECTRA OF POLYCYCLIC AROMATIC HYDROCARBON MOLECULES WITH ALIPHATIC SIDEGROUPS

The role of aliphatic side groups in the formation of astronomical unidentified infrared emission (UIE) features is investigated by applying the density functional theory to a series of molecules with mixed aliphatic-aromatic structures. The effects of introducing various aliphatic groups to a fixed polycyclic aromatic hydrocarbon (PAH) core (ovalene) are studied. Simulated spectra for each molecule are produced by applying a Drude profile at T = 500 K while the molecule is kept at its electronic ground state. The vibrational normal modes are classified using a semi-quantitative method. This allows us to separate the aromatic and aliphatic vibrations, and therefore provides clues to what types of vibrations are responsible for the emissions bands at different wavelengths. We find that many of the UIE bands are not pure aromatic vibrational bands but may represent coupled vibrational modes. The effects of aliphatic groups on the formation of the 8 μm plateau are quantitatively determined. The vibrational motions of methyl (–CH{sub 3}) and methylene (–CH{sub 2} –) groups can cause the merging of the vibrational bands of the parent PAH and the forming of broad features. These results suggest that aliphatic structures can play an important role in the UIE phenomenon.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2015

SULFUR-BEARING MOLECULES IN MASSIVE STAR-FORMING REGIONS: OBSERVATIONS OF OCS, CS, H{sub 2}S, AND SO

We studied the sulfur chemistry of massive star-forming regions through single-dish submillimeter spectroscopy. OCS, O{sup 13}CS, {sup 13}CS, H{sub 2}S, and SO transitions were observed toward a sample of massive star-forming regions with embedded UCH ii or CH ii regions. These sources could be divided into H ii-hot core and H ii-only sources based on their CH{sub 3}CN emission. Our results show that the OCS line of thirteen sources is optically thick, with optical depth ranging from 5 to 16. Column densities of these molecules were computed under LTE conditions. CS column densities were also derived using its optically thin isotopologue {sup 13}CS. H{sub 2}S is likely to be the most abundant gas-phase sulfuretted molecule in hot massive cores. Both the column density and abundance of sulfur-bearing molecules decrease significantly from H ii-hot core to H ii-only sources. Ages derived from hot core models appear to be consistent with star formation theories, suggesting that abundance ratios of [CS]/[SO], [SO]/[OCS], and [OCS]/[CS] could be used as chemical clocks in massive star-forming regions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Strongly aligned gas-phase molecules at free-electron lasers

Here, we demonstrate a novel experimental implementation to strongly align molecules at full repetition rates of free-electron lasers. We utilized the available in-house laser system at the coherent x-ray imaging beamline at the linac coherent light source. Chirped laser pulses, i.e., the direct output from the regenerative amplifier of the Ti:Sa chirped pulse amplification laser system, were used to strongly align 2, 5-diiodothiophene molecules in a molecular beam. The alignment laser pulses had pulse energies of a few mJ and a pulse duration of 94 ps. A degree of alignment of $\langle {\mathrm{cos}}^{2}{\theta }_{2{\rm{D}}}\rangle =0.85$ was measured, limited by the intrinsic temperature of the molecular beam rather than by the available laser system. With the general availability of synchronized chirped-pulse-amplified near-infrared laser systems at short-wavelength laser facilities, our approach allows for the universal preparation of molecules tightly fixed in space for experiments with x-ray pulses.

74 ATOMIC AND MOLECULAR PHYSICS↗