1
|
Yasumura S, Saita K, Miyakage T, Nagai K, Kon K, Toyao T, Maeno Z, Taketsugu T, Shimizu KI. Designing main-group catalysts for low-temperature methane combustion by ozone. Nat Commun 2023; 14:3926. [PMID: 37400448 DOI: 10.1038/s41467-023-39541-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 06/16/2023] [Indexed: 07/05/2023] Open
Abstract
The catalytic combustion of methane at a low temperature is becoming increasingly key to controlling unburned CH4 emissions from natural gas vehicles and power plants, although the low activity of benchmark platinum-group-metal catalysts hinders its broad application. Based on automated reaction route mapping, we explore main-group elements catalysts containing Si and Al for low-temperature CH4 combustion with ozone. Computational screening of the active site predicts that strong Brønsted acid sites are promising for methane combustion. We experimentally demonstrate that catalysts containing strong Bronsted acid sites exhibit improved CH4 conversion at 250 °C, correlating with the theoretical predictions. The main-group catalyst (proton-type beta zeolite) delivered a reaction rate that is 442 times higher than that of a benchmark catalyst (5 wt% Pd-loaded Al2O3) at 190 °C and exhibits higher tolerance to steam and SO2. Our strategy demonstrates the rational design of earth-abundant catalysts based on automated reaction route mapping.
Collapse
Affiliation(s)
- Shunsaku Yasumura
- Institute for Catalysis, Hokkaido University, N-21 W-10, Sapporo, Hokkaido, 001-0021, Japan
| | - Kenichiro Saita
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
| | - Takumi Miyakage
- Institute for Catalysis, Hokkaido University, N-21 W-10, Sapporo, Hokkaido, 001-0021, Japan
| | - Ken Nagai
- Institute for Catalysis, Hokkaido University, N-21 W-10, Sapporo, Hokkaido, 001-0021, Japan
| | - Kenichi Kon
- Institute for Catalysis, Hokkaido University, N-21 W-10, Sapporo, Hokkaido, 001-0021, Japan
| | - Takashi Toyao
- Institute for Catalysis, Hokkaido University, N-21 W-10, Sapporo, Hokkaido, 001-0021, Japan
| | - Zen Maeno
- School of Advanced Engineering, Kogakuin University, Tokyo, 192-0015, Japan
| | - Tetsuya Taketsugu
- Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo, Hokkaido, 060-0810, Japan
- Institute for Chemical Reaction Design and Discovery (WPI-ICReDD), Hokkaido University, Sapporo, Hokkaido, 001-0021, Japan
| | - Ken-Ichi Shimizu
- Institute for Catalysis, Hokkaido University, N-21 W-10, Sapporo, Hokkaido, 001-0021, Japan.
| |
Collapse
|
2
|
Shuman NS, Sweeny BC, Viggiano AA, Plane JMC, Feng W, Lachowicz A, Heaven MC, Ard SG. Kinetics of O 3 with Ca + and Its Higher Oxides CaO n+ ( n = 1-3) and Updates to a Model of Meteoric Calcium in the Mesosphere and Lower Thermosphere. J Phys Chem A 2023; 127:4043-4054. [PMID: 37115955 DOI: 10.1021/acs.jpca.3c01126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023]
Abstract
The room-temperature rate constants and product branching fractions of CaOn+ (n = 0-3) + O3 are measured using a selected ion flow tube apparatus. Ca+ + O3 produces CaO+ + O2 with k = 9 ± 4 × 10-10 cm3 s-1, within uncertainty equal to the Langevin capture rate constant. This value is significantly larger than several literature values. Most likely, those values were underestimated due to the reformation of Ca+ from the sequential chemistry of higher calcium oxide cations with O3, as explored here. A rate constant of 8 ± 3 × 10-10 cm3 s-1 is recommended. Both CaO+ and CaO2+ react near the capture rate constant with ozone. The CaO+ reaction yields both CaO2+ + O2 (0.80 ± 0.15 branching) and Ca+ + 2O2. Similarly, the CaO2+ reaction yields both CaO3+ + O2 (0.85 ± 0.15 branching) and CaO+ + 2O2. CaO3+ + O3 yield CaO2+ + 2O2 at 2 ± 1 × 10-11 cm3 s-1, about 2% of the capture rate constant. The results are supported using density functional calculations and statistical modeling. In general, CaOn+ + O3 yield CaOn+1+ + O2, the expected oxidation. Some fraction of CaOn+1+ is produced with sufficient internal energy to further dissociate to CaOn-1+ + O2, yielding the same products as the oxidation of O3 by CaOn+. Mesospheric Ca and Ca+ concentrations are modeled as functions of day, latitude, and altitude using the Whole Atmosphere Community Climate Model (WACCM); incorporating the updated rate constants improves agreement with concentrations derived from lidar measurements.
Collapse
Affiliation(s)
- Nicholas S Shuman
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Brendan C Sweeny
- Boston College Institute for Scientific Research, Boston, Massachusetts 02549, United States
| | - Albert A Viggiano
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - John M C Plane
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
| | - Wuhu Feng
- School of Chemistry, University of Leeds, Leeds LS2 9JT, U.K
- National Centre for Atmospheric Science and School of Earth and Environment, University of Leeds, Leeds LS2 9JT, U.K
| | - Anton Lachowicz
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Michael C Heaven
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Shaun G Ard
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| |
Collapse
|
3
|
Sweeny BC, Heaven MC, Lachowicz A, Johnson MA, Viggiano AA, Shuman NS, Ard SG. Gas-Phase Reactivity of Ozone with Lanthanide Ions (Sm +, Nd +) and Their Higher Oxides. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:1401-1410. [PMID: 35545264 DOI: 10.1021/jasms.2c00058] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The kinetics of SmOn+ (n = 0-2) and NdOn+ (n = 0-2) with O3 are measured using a selected-ion flow tube. Reaction of Nd+ to yield NdO+ + O2 occurs rapidly, with a rate constant near the capture-controlled limit of ∼8 × 10-10 cm3 s-1. NdO+ reacts at ∼40% of the capture limit to yield NdO2+ with little temperature dependence from 200 to 400 K. NdO2+ likely reacts very slowly (k ∼ 10-13 cm3 s-1) to yield NdO+ + 2O2, does not react to yield NdO3+, and associates slowly (k ∼ 10-12 cm3 s-1) to yield NdO2+(O3)1-3. Reaction of Sm+ also yields SmO+ at near the capture limit at all temperatures, but a significant fraction (∼50%) of the SmO+ is produced in excited states that are long-lived compared to the millisecond time scale of the experiment. These states are evidently resistant to both radiative and collisional relaxation. The excited-state production is likely due to a spin-conservation constraint on the reaction, despite the large spin-orbit coupling typical for lanthanide-containing species. Ground-state SmO+ reacts inefficiently (k = 2 × 10-11 (T/300)-2.5 cm3 s-1) to yield SmO2+ + O2, while the excited-state SmO+* reacts at the capture limit, with branching to yield Sm+ + 2O2 (ΔHr,0K = 148.7 ± 0.4 kJ mol-1 for ground-state SmO+) approximately 60% of the time, the remainder forming SmO2+, which further reacts with O3 to yield SmO+ at about 1% of the collisional value.
Collapse
Affiliation(s)
- Brendan C Sweeny
- Institute for Scientific Research, Boston College, Boston, Massachusetts 02467, United States
| | - Michael C Heaven
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
| | - Anton Lachowicz
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Mark A Johnson
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Albert A Viggiano
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland AFB, New Mexico 87117, United States
| | - Nicholas S Shuman
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland AFB, New Mexico 87117, United States
| | - Shaun G Ard
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland AFB, New Mexico 87117, United States
| |
Collapse
|
4
|
McDonald DC, Sweeny BC, Viggiano AA, Ard SG, Shuman NS. Cyclotrimerization of Acetylene under Thermal Conditions: Gas-Phase Kinetics of V + and Fe + + C 2H 2. J Phys Chem A 2021; 125:9327-9337. [PMID: 34665622 DOI: 10.1021/acs.jpca.1c06439] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The kinetics of successive reactions of acetylene (C2H2) initiated on either vanadium or iron atomic cations have been investigated under thermal conditions using the variable-ion source and temperature-adjustable selected-ion flow tube apparatus. Consistent with the literature results, the reaction of Fe+ + C2H2 primarily yields Fe+(m/z = (C2H2)3); however, analysis via quantum chemical calculations and statistical modeling shows that the mechanism does not form benzene upon the third acetylene addition. The kinetics are more consistent with successive addition of three acetylene molecules, yielding Fe+(C2H2)3, followed by an addition of a fourth acetylene molecule, initiating cyclotrimerization, yielding either Fe+(C2H2) + neutral benzene or Fe+(Bz) + acetylene, where Bz is a benzene ligand. In contrast, the reaction of V+ + C2H2 yields products via successive associations V+(m/z = (C2H2)n) either with or without a bimolecular step involving loss of one H2 and V+C2(m/z = (C2H2)m), where n and m extend at least up to 11 under conditions of 0.32 Torr at 300 K. Stabilized V+(Bz) is not a significant intermediate in the association mechanism. We propose a plausible mechanism for the generation of neutral benzene in this reaction and compare with the Fe+ results. The reaction steps that produce benzene result in turnover of the single-atom catalyst, and the large hydrocarbons produced that remain associated to the catalyst are proposed to be polycyclic aromatic hydrocarbons.
Collapse
Affiliation(s)
- David C McDonald
- NRC Postdoc at Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Brendan C Sweeny
- Institute for Scientific Research, Boston College, Boston, Massachusetts 02467, United States
| | - Albert A Viggiano
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Shaun G Ard
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Nicholas S Shuman
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| |
Collapse
|
5
|
Lockwood SP, Chunga T, Metz RB. Bonding, Thermodynamics, and Dissociation Dynamics of NiO + and NiS + Determined by Photofragment Imaging and Theory. J Phys Chem A 2021; 125:7425-7436. [PMID: 34427080 DOI: 10.1021/acs.jpca.1c05405] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We use photofragment ion imaging and ab initio calculations to determine the bond strength and photodissociation dynamics of the nickel oxide (NiO+) and nickel sulfide (NiS+) cations. NiO+ photodissociates broadly from 20350 to 32000 cm-1, forming ground state products Ni+(2D) + O(3P) below ∼29000 cm-1. Above this energy, Ni+(4F) + O(3P) products become accessible and dominate over the ground state channel. In certain images, product spin-orbit levels are resolved, and spin-orbit propensities are determined. Image anisotropy and the results of MRCI calculations suggest NiO+ photodissociates via a 3 4Σ- ← X 4Σ- transition above the Ni+(4F) threshold and via 3 4Σ-, 2 4Σ-, and/or 2 4Π and 3 4Π excited states below the 4F threshold. The photodissociation spectrum of NiS+ from 19900 to 23200 cm-1 is highly structured, with ∼12 distinct vibronic peaks, each containing underlying substructure. Above 21600 cm-1, the Ni+(2D5/2) + S(3P) and Ni+(2D3/2) + S(3P) product spin-orbit channels compete, with a branching ratio of ∼2:1. At lower energy, Ni+(2D5/2) is formed exclusively, and S(3P2) and S(3P1) spin-orbit channels are resolved. MRCI calculations predict the ground state of NiS+ to be one of two nearly degenerate states, the 1 4Σ- and 1 4Δ. Based on images and spectra, the ground state of NiS+ is assigned as 4Δ7/2, with the 1 4Σ3/2- and 1 4Σ1/2- states 81 ± 30 and 166 ± 50 cm-1 higher in energy, respectively. The majority of the photodissociation spectrum is assigned to transitions from the 1 4Δ state to two overlapping, predissociative excited 4Δ states. Our D0 measurements for NiO+ (D0 = 244.6 ± 2.4 kJ/mol) and NiS+ (D0 = 240.3 ± 1.4 kJ/mol) are more precise and closer to each other than previously reported values. Finally, using a recent measurement of D0(NiS), we derive a more precise value for IE (NiS): 8.80 ± 0.02 eV (849 ± 1.7 kJ/mol).
Collapse
Affiliation(s)
- Schuyler P Lockwood
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Tala Chunga
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| | - Ricardo B Metz
- Department of Chemistry, University of Massachusetts Amherst, Amherst, Massachusetts 01003, United States
| |
Collapse
|
6
|
Gao LG, Fleming DG, Truhlar DG, Xu X. Large Anharmonic Effects on Tunneling and Kinetics: Reaction of Propane with Muonium. J Phys Chem Lett 2021; 12:4154-4159. [PMID: 33890795 DOI: 10.1021/acs.jpclett.1c01229] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Calculations of kinetic isotope effects (KIEs) provide challenging tests of quantal mass effects on reaction rates, and muonium KIEs are the most challenging. Here, we show that it can be very important to include reaction-coordinate-dependent vibrational anharmonicity along the whole reaction path to calculate tunneling probabilities and KIEs. For the reaction of propane with Mu, this decreases both the height and width of the vibrationally adiabatic potential barrier, with both effects increasing the rate constants. Our results agree well with the experimental observations.
Collapse
Affiliation(s)
- Lu Gem Gao
- Center for Combustion Energy, Department of Energy and Power Engineering, and Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China
| | - Donald G Fleming
- TRIUMF and Department of Chemistry, University of British Columbia, 4004 Wesbrook Mall, Vancouver, BC V6T 1Z4, Canada
| | - Donald G Truhlar
- Department of Chemistry, Chemical Theory Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455-0431, United States
| | - Xuefei Xu
- Center for Combustion Energy, Department of Energy and Power Engineering, and Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Tsinghua University, Beijing 100084, China
| |
Collapse
|
7
|
Ard SG, Viggiano AA, Shuman NS. Old School Techniques with Modern Capabilities: Kinetics Determination of Dynamical Information Such as Barriers, Multiple Entrance Channel Complexes, Product States, Spin Crossings, and Size Effects in Metallic Ion–Molecule Reactions. J Phys Chem A 2021; 125:3503-3527. [DOI: 10.1021/acs.jpca.0c11395] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Shaun G. Ard
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Albert A. Viggiano
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| | - Nicholas S. Shuman
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Albuquerque, New Mexico 87117, United States
| |
Collapse
|
8
|
Bones DL, Daly SM, Mangan TP, Plane JMC. A study of the reactions of Ni + and NiO + ions relevant to planetary upper atmospheres. Phys Chem Chem Phys 2020; 22:8940-8951. [PMID: 32292965 DOI: 10.1039/d0cp01124j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reactions between Ni+(2D) and O3, O2, N2, CO2 and H2O were studied at 294 K using the pulsed laser ablation at 532 nm of a nickel metal target in a fast flow tube, with mass spectrometric detection of Ni+ and NiO+. The rate coefficient for the reaction of Ni+ with O3 is k(294 K) = (9.7 ± 2.1) × 10-10 cm3 molecule-1 s-1; the reaction proceeds at the ion-permanent dipole enhanced Langevin capture rate with a predicted T-0.16 dependence. Electronic structure theory calculations were combined with Rice-Ramsperger-Kassel-Markus theory to extrapolate the measured recombination rate coefficients to the temperature and pressure conditions of planetary upper atmospheres. The following low-pressure limiting rate coefficients were obtained for T = 120-400 K and He bath gas (in cm6 molecule-2 s-1, uncertainty ±σ at 180 K): log10(k, Ni+ + N2) = -27.5009 + 1.0667log10(T) - 0.74741(log10(T))2, σ = 29%; log10(k, Ni+ + O2) = -27.8098 + 1.3065log10(T) - 0.81136(log10(T))2, σ = 32%; log10(k, Ni+ + CO2) = -29.805 + 4.2282log10(T) - 1.4303(log10(T))2, σ = 28%; log10(k, Ni+ + H2O) = -24.318 + 0.20448log10(T) - 0.66676(log10(T))2, σ = 28%). Other rate coefficients measured (at 294 K, in cm3 molecule-1 s-1) were: k(NiO+ + O) = (1.7 ± 1.2) × 10-10; k(NiO+ + CO) = (7.4 ± 1.3) × 10-11; k(NiO+ + O3) = (2.7 ± 1.0) × 10-10 with (29 ± 21)% forming Ni+ as opposed to NiO2+; k(NiO2+ + O3) = (2.9 ± 1.4) × 10-10, with (16 ± 9)% forming NiO+ as opposed to ONiO2+; and k(Ni+·N2 + O) = (7 ± 4) × 10-12. The chemistry of Ni+ and NiO+ in the upper atmospheres of Earth and Mars is then discussed.
Collapse
Affiliation(s)
- David L Bones
- School of Chemistry, University of Leeds, Leeds, UK.
| | - Shane M Daly
- School of Chemistry, University of Leeds, Leeds, UK.
| | | | | |
Collapse
|
9
|
Sweeny BC, Pan H, Kassem A, Sawyer JC, Ard SG, Shuman NS, Viggiano AA, Brickel S, Unke OT, Upadhyay M, Meuwly M. Thermal activation of methane by MgO+: temperature dependent kinetics, reactive molecular dynamics simulations and statistical modeling. Phys Chem Chem Phys 2020; 22:8913-8923. [DOI: 10.1039/d0cp00668h] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The kinetics methane activation (MgO+ + CH4) was studied experimentally and computationally by running and analyzing reactive atomistic simulations.
Collapse
Affiliation(s)
- Brendan C. Sweeny
- NRC Postdoc at Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | - Hanqing Pan
- USRA Space Scholar at Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | - Asmaa Kassem
- USRA Space Scholar at Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | - Jordan C. Sawyer
- NRC Postdoc at Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | - Shaun G. Ard
- Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | - Nicholas S. Shuman
- Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | - Albert A. Viggiano
- Air Force Research Laboratory
- Space Vehicles Directorate
- Kirtland Air Force Base
- USA
| | | | - Oliver T. Unke
- Department of Chemistry
- University of Basel
- CH-4056 Basel
- Switzerland
| | - Meenu Upadhyay
- Department of Chemistry
- University of Basel
- CH-4056 Basel
- Switzerland
| | - Markus Meuwly
- Department of Chemistry
- University of Basel
- CH-4056 Basel
- Switzerland
| |
Collapse
|
10
|
Sweeny BC, Pan H, Ard SG, Shuman NS, Viggiano AA. On the Role of Hydrogen Atom Transfer (HAT) in Thermal Activation of Methane by MnO+: Entropy vs. Energy. ACTA ACUST UNITED AC 2019. [DOI: 10.1515/zpch-2018-1354] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Abstract
The temperature dependent kinetics and product branching fractions of first-row transition metal oxide cation MnO+ with CH4 and CD4 at temperatures between 200 and 600 K are measured using a selected-ion flow tube apparatus. Likely reaction mechanisms are determined by comparison of temperature dependent kinetics to statistical modeling along calculated reaction coordinates. The data is well-modeled with the reaction proceeding over a rate limiting four-centered transition state leading to an insertion intermediate, similar to reactions of NiO+ and FeO+, and showing characteristics of proton-coupled electron transfer (PCET). However, a more direct pathway traversing a transition state of hydrogen atom transfer (HAT) character to a hydroxyl intermediate is found to possibly be competitive, especially with increasing temperature. While uncertainties in calculated energetics limit quantitative assessment of the role of HAT at thermal energies, it is clear that this mechanism becomes increasingly prevalent in higher energy regimes.
Collapse
Affiliation(s)
- Brendan C. Sweeny
- NRC postdoc at Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base , New Mexico 87117 , USA
| | - Hanqing Pan
- USRA Space Scholar at Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base , New Mexico 87117 , USA
| | - Shaun G. Ard
- Institute for Scientific Research, Boston College , Boston, MA 02467 , USA
| | - Nicholas S. Shuman
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base , New Mexico 87117 , USA
| | - Albert A. Viggiano
- Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base , New Mexico 87117 , USA
| |
Collapse
|