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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Ho(Ni2P)2 by Materials Project

Ho(Ni2P)2 crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. Ho is bonded in a 6-coordinate geometry to six equivalent P atoms. There are two shorter (2.79 Å) and four longer (2.83 Å) Ho–P bond lengths. Ni is bonded in a 3-coordinate geometry to three equivalent P atoms. There are two shorter (2.30 Å) and one longer (2.31 Å) Ni–P bond lengths. P is bonded in a 9-coordinate geometry to three equivalent Ho and six equivalent Ni atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2021

On the Rate Constant for NH 2 +HO 2 and Third-Body Collision Efficiencies for NH 2 +H(+M) and NH 2 +NH 2 (+M)

In low-temperature flash photolysis of NH 3 /O 2 /N 2 mixtures, the NH 2 consumption rate and the product distribution is controlled by the reactions NH 2 + HO 2 → products (R1), NH 2 + H (+M) → NH 3 (+M) (R2), and NH 2 + NH 2 (+M) → N 2 H 4 (+M) (R3). In the present work, published flash photolysis experiments by, among others, Cheskis and co-workers, are re-interpreted using recent direct measurements of NH 2 + H (+N 2 ) and NH 2 + NH 2 (+N 2 ) from Altinay and Macdonald. To facilitate analysis of the FP data, relative third-body collision efficiencies compared to N 2 for R2 and R3 were calculated for O 2 and NH 3 as well as for other selected molecules. We report results were in good agreement with the limited experimental data. Based on reported NH 2 decay rates in flash photolysis of NH 3 /O 2 /N 2 , a rate constant for NH 2 + HO 2 → NH 3 + O 2 (R1a) of $k_{1\text{a}}$ = 1.5(±0.5) × 10 14 cm 3 mol –1 s –1 at 295 K was derived. This value is higher than earlier determinations based on the FP results but in good agreement with recent theoretical work. Kinetic modeling of reported N 2 O yields indicates that NH 2 + HO 2 → H 2 NO + O (R1c) is competing with R1a, but perturbation experiments with addition of CH4 indicate that it is not a dominating channel. Measured HNO profiles indicate that this component is formed directly by NH 2 + HO 2 → HNO + H 2 O (R1b), but theoretical work indicates that R1b is only a minor channel. Based on this analysis, we estimate $k_{1\text{c}}$ = 2.5 × 10 13 cm 3 mol –1 s –1 and $k_{1\text{b}}$ = 2.5 × 10 12 cm 3 mol –1 s –1 at 295 K, with significant uncertainty margins.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Energy transfer processes between Tm(3+) and Ho(3+) in LiYF4

The spectroscopic properties of the crystal LiYF4 doped with Thulium (Tm) and Holmium (Ho) ions are studied. The basic processes are discussed that regulate the transfer of energy between these two ions in this crystal. In this system Tm is considered the donor ion and the Ho the acceptor ion. Spectral data were obtained on three samples available: LiYF4:Tm(3+) (0.5 percent), LiYF4:Ho(3+) (1 percent), and LiYF4:Tm(3+) (5 percent), Ho(3+) (0.2 percent). Spectral data, which include absorption, luminescence, excitation, and the response to pulsed excitation in a wide range of temperatures, allowed to look at the energy transfer processes by considering the kinetic evolution of the emission of the two ions (donor and acceptor) involved in the process and the basic spectroscopic properties related to them. This inclusive approach has led to the validation of the physical model.

Oezen, Goenuel↗
NASA NTRS1990

Simultaneous, in situ measurements of OH, HO2, O3, and H2O - A test of modeled stratospheric HO(x) chemistry

Simultaneous, in situ measurements of OH, HO2, H2O, and O3 from 37-23 km are reported. The partitioning between OH and HO2 and the total HO(x) concentration are compared with expected steady-state values. The ratio of HO2 to OH varies from less than 2 at 36 km to more than 3 at 25 km; in the lower stratosphere this ratio is nearly a factor of two less than predicted. The data are used to calculate HO(x) production and loss rates. The measured HO(x) mixing ratio is consistent with production dominated by the reaction of O(1D) with H2O, and loss controlled by NOy below 28 km and HO(x) above 30 km. The steady-state concentration of H2O2 is inferred from the measured HO2 concentration and calculated photolysis rate. The maximum H2O2 mixing ratio (at 33 km) is predicted to be less than 0.2 ppb.

Wennberg, P. O.↗
NASA NTRS1991

Injection-seeded operation of a Q-switched Cr,Tm,Ho:YAG laser

Single-frequency Tm,Ho:YAG lasers operating near 2 microns are attractive sources for several applications including eye-safe laser radar (lidar) and pumping of AgGaSe2 parametric oscillators for efficient generation of longer wavelengths. As part of a program to develop a coherent lidar system using Tm,Ho:YAG lasers, a diode laser-pumped tunable CW single-longitudinal-mode (SLM) Cr:Tm:Ho:YAG laser and a flashlamp-pumped single-transverse-mode Q-switched Cr,Tm,Ho:YAG laser were developed. The CW laser was used to injection-seed the flashlamp-pumped laser, resulting in SLM Q-switched output. Operational characteristics of the CW and Q-switched lasers and injection-seeding results are reported.

Henderson, Sammy W.↗
DOE OSTI2020

Materials Data on Ho(AlCl4)3 by Materials Project

Ho(AlCl4)3 crystallizes in the trigonal P3_112 space group. The structure is one-dimensional and consists of one Ho(AlCl4)3 ribbon oriented in the (0, 0, 1) direction. Ho3+ is bonded in a 8-coordinate geometry to eight Cl1- atoms. There are a spread of Ho–Cl bond distances ranging from 2.72–2.92 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Cl1- atoms. There are two shorter (2.16 Å) and two longer (2.17 Å) Al–Cl bond lengths. In the second Al3+ site, Al3+ is bonded in a tetrahedral geometry to four Cl1- atoms. There are a spread of Al–Cl bond distances ranging from 2.10–2.24 Å. There are six inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Ho3+ and one Al3+ atom. In the second Cl1- site, Cl1- is bonded in a single-bond geometry to one Al3+ atom. In the third Cl1- site, Cl1- is bonded in a single-bond geometry to one Al3+ atom. In the fourth Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Ho3+ and one Al3+ atom. In the fifth Cl1- site, Cl1- is bonded in a distorted L-shaped geometry to one Ho3+ and one Al3+ atom. In the sixth Cl1- site, Cl1- is bonded in an L-shaped geometry to one Ho3+ and one Al3+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(MnGe)2 by Materials Project

HoMn2Ge2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ho is bonded in a 8-coordinate geometry to eight equivalent Ge atoms. All Ho–Ge bond lengths are 3.06 Å. Mn is bonded to four equivalent Ge atoms to form a mixture of corner and edge-sharing MnGe4 tetrahedra. All Mn–Ge bond lengths are 2.43 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ho, four equivalent Mn, and one Ge atom. The Ge–Ge bond length is 2.57 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(NO3)3 by Materials Project

Ho(NO3)3 crystallizes in the monoclinic P2_1/c space group. The structure is two-dimensional and consists of one Ho(NO3)3 sheet oriented in the (0, 0, 1) direction. Ho3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.34–2.68 Å. There are three inequivalent N5+ sites. In the first N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.26–1.28 Å. In the second N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.26 Å) and two longer (1.27 Å) N–O bond length. In the third N5+ site, N5+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of N–O bond distances ranging from 1.24–1.31 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ho3+ and one N5+ atom. In the second O2- site, O2- is bonded in a distorted L-shaped geometry to one Ho3+ and one N5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ho3+ and one N5+ atom. In the fourth O2- site, O2- is bonded in a distorted single-bond geometry to one Ho3+ and one N5+ atom. In the fifth O2- site, O2- is bonded in a distorted L-shaped geometry to one Ho3+ and one N5+ atom. In the sixth O2- site, O2- is bonded in a single-bond geometry to one Ho3+ and one N5+ atom. In the seventh O2- site, O2- is bonded in a distorted single-bond geometry to one Ho3+ and one N5+ atom. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+ and one N5+ atom. In the ninth O2- site, O2- is bonded in a distorted L-shaped geometry to one Ho3+ and one N5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(CuS)3 by Materials Project

Ho(CuS)3 crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one Ho(CuS)3 sheet oriented in the (0, 0, 1) direction. Ho3+ is bonded to six S2- atoms to form HoS6 octahedra that share corners with nine CuS4 tetrahedra, edges with six equivalent HoS6 octahedra, and edges with six CuS4 tetrahedra. There are three shorter (2.72 Å) and three longer (2.84 Å) Ho–S bond lengths. There are three inequivalent Cu1+ sites. In the first Cu1+ site, Cu1+ is bonded to four equivalent S2- atoms to form CuS4 tetrahedra that share corners with six equivalent HoS6 octahedra, corners with six equivalent CuS4 tetrahedra, edges with three equivalent HoS6 octahedra, and edges with three equivalent CuS4 tetrahedra. The corner-sharing octahedra tilt angles range from 22–52°. There are three shorter (2.34 Å) and one longer (2.48 Å) Cu–S bond lengths. In the second Cu1+ site, Cu1+ is bonded in a trigonal planar geometry to three equivalent S2- atoms. All Cu–S bond lengths are 2.25 Å. In the third Cu1+ site, Cu1+ is bonded to four S2- atoms to form CuS4 tetrahedra that share corners with three equivalent HoS6 octahedra, corners with six equivalent CuS4 tetrahedra, and edges with three equivalent HoS6 octahedra. The corner-sharing octahedral tilt angles are 12°. There are one shorter (2.27 Å) and three longer (2.43 Å) Cu–S bond lengths. There are three inequivalent S2- sites. In the first S2- site, S2- is bonded to three equivalent Ho3+ and four equivalent Cu1+ atoms to form distorted SHo3Cu4 pentagonal bipyramids that share corners with three equivalent SHo3Cu3 octahedra, edges with three equivalent SHo3Cu3 octahedra, and edges with nine equivalent SHo3Cu4 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 3°. In the second S2- site, S2- is bonded to three equivalent Ho3+ and three equivalent Cu1+ atoms to form distorted SHo3Cu3 octahedra that share corners with three equivalent SHo3Cu4 pentagonal bipyramids, corners with three equivalent SCu4 trigonal pyramids, edges with six equivalent SHo3Cu3 octahedra, and edges with three equivalent SHo3Cu4 pentagonal bipyramids. In the third S2- site, S2- is bonded to four Cu1+ atoms to form SCu4 trigonal pyramids that share corners with three equivalent SHo3Cu3 octahedra and corners with six equivalent SCu4 trigonal pyramids. The corner-sharing octahedral tilt angles are 68°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(AsO)2 by Materials Project

Ho(AsO)2 crystallizes in the tetragonal I4_1/amd space group. The structure is zero-dimensional and consists of eight Ho(AsO)2 clusters. Ho3+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ho–O bond lengths are 2.11 Å. As+0.50+ is bonded in a single-bond geometry to one O2- atom. The As–O bond length is 1.78 Å. O2- is bonded in a distorted linear geometry to one Ho3+ and one As+0.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(PO)2 by Materials Project

Ho(PO)2 crystallizes in the tetragonal I4_1/amd space group. The structure is zero-dimensional and consists of eight Ho(PO)2 clusters. Ho3+ is bonded in a linear geometry to two equivalent O2- atoms. Both Ho–O bond lengths are 2.20 Å. P+0.50+ is bonded in a single-bond geometry to one O2- atom. The P–O bond length is 1.58 Å. O2- is bonded in a water-like geometry to one Ho3+ and one P+0.50+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on AlZn2Sb(HO)12 by Materials Project

Zn2Al(OH)6Sb(HO)6 crystallizes in the trigonal P-3 space group. The structure is two-dimensional and consists of one Sb(HO)6 cluster and one Zn2Al(OH)6 sheet oriented in the (0, 0, 1) direction. In the Sb(HO)6 cluster, Sb5+ is bonded in an octahedral geometry to six equivalent O2- atoms. All Sb–O bond lengths are 2.01 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. O2- is bonded in a distorted single-bond geometry to one Sb5+ and one H1+ atom. In the Zn2Al(OH)6 sheet, Zn2+ is bonded to six equivalent O2- atoms to form ZnO6 octahedra that share edges with three equivalent ZnO6 octahedra and edges with three equivalent AlO6 octahedra. There are three shorter (2.13 Å) and three longer (2.17 Å) Zn–O bond lengths. Al3+ is bonded to six equivalent O2- atoms to form AlO6 octahedra that share edges with six equivalent ZnO6 octahedra. All Al–O bond lengths are 1.93 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.98 Å. O2- is bonded in a 1-coordinate geometry to two equivalent Zn2+, one Al3+, and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Kinetic study of reaction C 2 H 5 + HO 2 in a photolysis reactor with time-resolved Faraday rotation spectroscopy

The rate constant and branching ratios of ethyl reaction with hydroperoxyl radical, C 2 H 5 + HO 2 (1), a key radical-radical reaction for intermediate temperature combustion chemistry, were measured in situ for the first time in a photolysis Herriott cell by using mid-IR Faraday rotation spectroscopy (FRS) and UV-IR direct absorption spectroscopy (DAS). The microsecond time-resolved diagnostic technique in this work enabled the direct rate measurements of the target reaction at 40 and 80 mbar and reduced the experimental uncertainty considerably. C 2 H 5 and HO 2 radicals were generated by the photolysis of (COCl) 2 /C 2 H 5 I/CH 3 OH/O 2 /He mixture at 266 nm. By direct measurements of the transient profiles of C 2 H 5 , HO 2 and OH concentrations, the overall rate constant for this reaction at 297 K was determined as k 1 (40 mbar) = (3.8 ± 0.8) × 10 –11 cm 3 molecule –1 s –1 and k 1 (80 mbar) = (4.1 ± 1.0) × 10 –11 cm 3 molecule –1 s –1 . As a result, the direct observation of hydroxyl radical (OH) indicated that OH formation channel was the major channel with a branching ratio of 0.8 ± 0.1.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

High-Temperature Reaction Kinetics of the e aq – and HO 2 • Radicals with Iron(II) Ions in Aqueous Solutions

Pulsed electron radiolysis was used to determine the chemical reaction kinetics and Arrhenius parameters for iron(II) reactions in aqueous solutions under irradiation. The second-order Fe 2+ reactions with the hydrated electron (e aq – ) and the perhydroxyl radical (HO 2 • ), arising from water radiolysis, were measured to high temperatures using custom-built flow-through cells with a multichannel optical detection system. The reaction with the HO 2 • radical was found to proceed via the formation of a metal-ion adduct species, Fe 2+ –HO 2 • . Additionally, the adduct’s molar extinction coefficient and its first-order decay rate coefficients are reported.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2025

2D photofragmentation LIF imaging of H 2 O 2 and HO 2 in the effluent of an atmospheric-pressure plasma jet: effects of solid and liquid interfaces

Two-dimensional (2D) absolute measurements of hydrogen peroxide (H 2 O 2 ) and approximations of the hydroperoxyl radical (HO 2 ) in the effluent of a COST Reference Microplasma Jet operated with a He/H 2 O feed gas are presented. Gas-phase densities are mapped using photofragmentation laser-induced fluorescence (PF-LIF) under three boundary conditions: open effluent, a solid target, and a liquid target. A novel method is presented for separating PF-LIF signals from H 2 O 2 and HO 2 using comparative measurements in oxygen-rich and oxygen-free environments to exploit the preferential formation of HO 2 in the presence of molecular oxygen. This separation strategy is supported by results from a plug-flow plasma chemistry model. Measured densities agree closely with model predictions in both magnitude and trend, while the 2D experimental distributions provide additional insight into the spatial dependencies of these species. In particular, the results show distinct differences in species transport depending on the target type: solid surfaces induce lateral deflection and reduced centerline densities, whereas liquid interfaces promote axial accumulation and higher near-axis concentrations.

atmospheric-pressure plasma jet (APPJ)↗
DOE OSTI2020

Isomeric and beta-decay spectroscopy of 173,174 Ho

β-decay spectroscopy of 173,174 Ho (Z = 67, N = 106,107) was conducted at Radioactive Isotope Beam Factory at RIKEN by using in-flight fission of a 345-MeV/u 238 U primary beam. A previously unreported isomeric state at 405 keV with half-life of 3.7(12) μs and a spin and parity of (3/2 + ) is identified in 173 Ho. Moreover, a new state with a spin and parity of 9 - was discovered in 174 Er. The experimental log ft values of 5.84(20) and 5.25(18) suggest an allowed-hindered β decay from the ground state of 174 Ho to the K π = 8 - isomeric state in 174 Er. Configuration-constrained potential energy surface (PES) calculations were performed and the predictions are in reasonable agreement with the experimental results.

150 ≤ A ≤ 189↗
DOE OSTI2023

Vibronic Relaxation Pathways in Molecular Spin Qubit Na 9 [Ho(W 5 O 18 ) 2 ]·35H 2 O under Pressure

In order to explore how spectral sparsity and vibronic decoherence pathways can be controlled in a model qubit system with atomic clock transitions, we combined diamond anvil cell techniques with synchrotron-based far infrared spectroscopy and first-principles calculations to reveal the vibrational response of Na 9 [Ho(W 5 O 18 ) 2 ]·35H 2 O under compression. Because the hole in the phonon density of states acts to reduce the overlap between the phonons and f manifold excitations in this system, we postulated that pressure might move the HoO 4 rocking, bending, and asymmetric stretching modes that couple with the M J = ±5, ±2, and ±7 levels out of resonance, reducing their interactions and minimizing decoherence processes, while a potentially beneficial strategy for some molecular qubits, pressure slightly hardens the phonons in Na 9 [Ho(W 5 O 18 ) 2 ]·35H 2 O and systematically fills in the transparency window in the phonon response. The net result is that the vibrational spectrum becomes less sparse and the overlap with the various M J levels of the Ho 3+ ion actually increases. These findings suggest that negative pressure, achieved using chemical means or elongational strain, could further open the transparency window in this rare earth-containing spin qubit system, thus paving the way for the use of device surfaces and interface elongational/compressive strains to better manage decoherence pathways.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Tm,Ho:YLF laser end-pumped by a semiconductor diode laser array

An Ho:YLF crystal including Tm as sensitizers for the activator Ho, is optically pumped with a semiconductor diode laser array to generate 2.1 micron radiation with a pump power to output power of efficiency as high as 68 percent. The prior-art dual sensitizer system of Er and Tm requires cooling, such as by LN2, but by using Tm alone and decreasing the concentrations of Tm and Ho, and decreasing the length of the laser rod to about 1 cm, it has been demonstrated that laser operation can be obtained from a temperature of 77 K with an efficiency as high as 68 percent up to ambient room temperature with an efficiency at that temperature as high as 9 percent.

Hemmati, Hamid↗