Reactive pathways in the bromobenzene-ammonia dimer cation radical: Evidence for a roaming halogen radical
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Nyambo, Silver↗
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Results for “ROAMS”
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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OH Roaming and Beyond in the Unimolecular Decay of the Methyl-Ethyl-Substituted Criegee Intermediate: Observations and Predictions
Alkene ozonolysis generates short-lived Criegee intermediates that are a significant source of hydroxyl (OH) radicals. Here this study demonstrates that roaming of the separating OH radicals can yield alternate hydroxycarbonyl products, thereby reducing the OH yield. Specifically, hydroxybutanone has been detected as a stable product arising from roaming in the unimolecular decay of the methyl-ethyl-substituted Criegee intermediate (MECI) under thermal flow cell conditions. The dynamical features of this novel multistage dissociation plus a roaming unimolecular decay process have also been examined with ab initio kinetics calculations. Experimentally, hydroxybutanone isomers are distinguished from the isomeric MECI by their higher ionization threshold and distinctive photoionization spectra. Moreover, the exponential rise of the hydroxybutanone kinetic time profile matches that for the unimolecular decay of MECI. A weaker methyl vinyl ketone (MVK) photoionization signal is also attributed to OH roaming. Complementary multireference electronic structure calculations have been utilized to map the unimolecular decay pathways for MECI, starting with 1,4 H atom transfer from a methyl or methylene group to the terminal oxygen, followed by roaming of the separating OH and butanonyl radicals in the long-range region of the potential. Roaming via reorientation and the addition of OH to the vinyl group of butanonyl is shown to yield hydroxybutanone, and subsequent C–O elongation and H-transfer can lead to MVK. A comprehensive theoretical kinetic analysis has been conducted to evaluate rate constants and branching yields (ca. 10–11%) for thermal unimolecular decay of MECI to conventional and roaming products under laboratory and atmospheric conditions, consistent with the estimated experimental yield (ca. 7%).
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
OH Roaming during the Ozonolysis of α-Pinene: A New Route to Highly Oxygenated Molecules?
The formation of low-volatility organic compounds in the ozonolysis of α-pinene, the dominant atmospheric monoterpene, provides an important route to aerosol formation. Here, in this work, we consider a previously unexplored set of pathways for the formation of highly oxygenated molecules in α-pinene ozonolysis. Pioneering, direct experimental observations of Lester and co-workers have demonstrated a significant production of hydroxycarbonyl products in the dissociation of Criegee intermediates. Theoretical analyses indicate that this production arises from OH roaming-induced pathways during the OO fission of the vinylhydroperoxides (VHPs), which in turn come from internal H transfers in the Criegee intermediates. Ab initio kinetics computations are used here to explore the OH roaming-induced channels that arise from the ozonolysis of α-pinene. For computational reasons, the calculations consider a surrogate for α-pinene, where two spectator methyl groups are replaced with H atoms. Multireference electronic structure calculations are used to illustrate a variety of energetically accessible OH roaming pathways for the four VHPs arising from the ozonolysis of this α-pinene surrogate. Ab initio transition-state theory-based master equation calculations indicate that for the dissociation of stabilized VHPs, these OH roaming pathways are kinetically significant with a branching that generally increases from ~20% at room temperature up to ~70% at lower temperatures representative of the troposphere. For one of the VHPs, this branching already exceeds 60% at room temperature. For the overall ozonolysis process, these branching ratios would be greatly reduced by a limited branching to the stabilized VHP, although there would also be some modest roaming fraction for the nonthermal VHP dissociation process. The strong exothermicities of the roaming-induced isomerizations/additions and abstractions suggest new routes to fission of the cyclobutane rings. Such ring fissions would facilitate further autoxidation reactions, thereby providing a new route for producing highly oxygenated nonvolatile precursors to aerosol formation.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Generating CAHV and CAHVOR Images with Shadows in ROAMS
Part of the Rover Analysis, Modeling and Simulation (ROAMS) software that synthesizes images of terrain has been augmented to make the images more realistic. [ROAMS was described in "Simulating Operation of a Planetary Rover" (NPO-30722), NASA Tech Briefs, Vol. 28, No. 9 (September 2004), page 52. ROAMS simulates the operation of a robotic vehicle (rover) exploring terrain on a remote planet.] The images are needed for modeling responses of rover cameras that provide sensory inputs for machine-vision-based algorithms for controlling the motion of the rover. The augmented image-synthesizing part of the ROAMS software supports terrain geometry and texture specifiable by the user, CAHV and CAHVOR camera models, and more-realistic shadowing (see figure). (The letters in "CAHV" represent vectors in a standard photogrammetric model of a pinhole camera. Letters O and R in "CAHVOR" represent vectors used to model distortions.) A contemplated future version of ROAMS would support the CAHVORE model, which represents more-general cameras, including those having fish-eye or other wide-field-of-view lenses. (Letter E in "CAHVORE" represents a vector used to model apparent motion of a camera entrance pupil.)
Madison, Richard↗
Building a Trusted Roaming Hub [Slides]
The Trusted Roaming Hub is a U.S. Department of Energy-backed initiative led by the National Laboratory of the Rockies (NLR) to address one of the most persistent challenges in electric vehicle (EV) charging: fragmented roaming, inconsistent interoperability, and insufficient digital trust across charging networks. As EV adoption accelerates and charging infrastructure scales nationwide, today's many-to-many integration model between eMobility Service Providers (eMSPs) and Charge Point Operators (CPOs) has become increasingly brittle, costly, and difficult to secure. The Trusted Roaming Hub introduces a neutral, cybersecurity-forward "switchboard" architecture that enables standardized, secure, and scalable roaming interactions across the EV charging ecosystem. Rather than replacing existing networks or commercial relationships, the hub acts as a trusted intermediary that enforces consistent identity, authentication, authorization, and routing across participants improving reliability for drivers, lowering integration burden for industry, and creating a foundation for future grid-interactive charging services. This read-ahead provides an overview of the problem the hub is designed to solve, the core functional and security concepts behind the architecture, the value proposition to key stakeholders, and the near-term trajectory of the work.
33 ADVANCED PROPULSION SYSTEMS↗
Development and Demonstration of a Wideband RF User Terminal for Roaming between Ka-band Relay Satellite Networks
The National Aeronautics and Space Administration (NASA) has provided low-latency communication relay services to science and exploration spacecraft for nearly four decades with the Tracking and Data Relay Satellite System (TDRSS). Through NASA’s Communications Services Project (CSP), the agency is pursuing a transition away from dedicated government-owned communication relay satellites and infrastructure in favour of commercially provided satellite communication (SATCOM) services. Many of these SATCOM services are offered in the K/Ka-band covering spectrum allocated to commercial, military, and civilian space operations. While these services were intended to provide broadband connectivity for terrestrial, maritime, and aviation customers, many can be tailored to support orbiting spacecraft. By introducing commercial SATCOM providers, NASA intends to create an interoperable network of networks which will enable missions to roam between multiple service providers. A key enabling technology needed for this vision is a multi-frequency (wideband), multi-waveform user terminal which can seamlessly roam between multiple providers. This paper discusses the development and ground demonstration of a new wideband RF user terminal prototype designed to roam across multiple networks over the Ka-band, allowing ubiquitous service, resiliency, and flexibility for the user.
satellite communication↗
H2 roaming chemistry and the formation of H3+ from organic molecules in strong laser fields
Roaming mechanisms, involving the brief generation of a neutral atom or molecule that stays in the vicinity before reacting with the remaining atoms of the precursor, are providing valuable insights into previously unexplained chemical reactions. Here in this paper, the mechanistic details and femtosecond time-resolved dynamics of H 3 + formation from a series of alcohols with varying primary carbon chain lengths are obtained through a combination of strong-field laser excitation studies and ab initio molecular dynamics calculations. For small alcohols, four distinct pathways involving hydrogen migration and H 2 roaming prior to H 3 + formation are uncovered. Despite the increased number of hydrogens and possible combinations leading to H 3 + formation, the yield decreases as the carbon chain length increases. The fundamental mechanistic findings presented here explore the formation of H 3 +, the most important ion in interstellar chemistry, through H 2 roaming occurring in ionic species.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Formaldehyde roaming dynamics: Comparison of quasi-classical trajectory calculations and experiments
The photodissociation dynamics of roaming in formaldehyde are studied by comparing quasi-classical trajectory calculations performed on a new potential energy surface (PES) to new and detailed experimental results detailing the CO + H 2 product state distributions and their correlations. The new PES proves to be a significant improvement over the past one, now more than a decade old. The new experiments probe both the CO and H 2 products of the formaldehyde dissociation. The experimental and trajectory data offer unprecedented detail about the correlations between internal states of the CO and H 2 dissociation products as well as information on how these distributions are different for the roaming and transition-state pathways. The data investigated include, for dissociation on the formaldehyde 2143 band, the speed distributions for individual vibrational/rotational states of the CO products, providing information about the correlated internal energy distributions of the H 2 product, and the rotational and vibrational distributions for the CO and H 2 products as well as the contributions to each from both the transition state and roaming channels. The agreement between the trajectory and experimental data is quite satisfactory, although minor differences are noted. In conclusion, the general agreement provides support for future use of the experimental techniques and the new PES in understanding the dynamics of photodissociative processes.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Substituent effects on H 3 + formation via H 2 roaming mechanisms from organic molecules under strong-field photodissociation
Roaming chemical reactions are often associated with neutral molecules. The recent findings of roaming processes in ionic species, in particular, ones that lead to the formation of H 3+ under strong-field laser excitation, are of considerable interest. Given that such gas-phase reactions are initiated by double ionization and subsequently facilitated through deprotonation, in this work we investigate the strong-field photodissociation of ethanethiol, also known as ethyl mercaptan, and compare it to results from ethanol. Contrary to expectations, the H 3+ yield was found to be an order of magnitude lower for ethanethiol at certain laser field intensities, despite its lower ionization energy and higher acidity compared to ethanol. In-depth analysis of the femtosecond time-resolved experimental findings, supported by ab initio quantum mechanical calculations, provides key information regarding the roaming mechanisms related to H 3+ formation. Results of this study on the dynamics of dissociative half-collisions involving H 3+ , a vital cation which acts as a Brønsted–Lowry acid protonating interstellar organic compounds, may also provide valuable information regarding the formation mechanisms and observed natural abundances of complex organic molecules in interstellar media and planetary atmospheres.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Recent developments in the ROAMS planetary rover simulation environment
This paper describes recent developments in the ROAMS physics-based simulator for planetary surface exploration rover vehicles. ROAMS includes models for various subsystems and components of the robotic vehicle including its mechanical subsystem, sensors, on-board resources, on-board control software, the terrain environment and terrain/vehicle interactions. The ROAMS simulator can be used for stand-alone simulation, closed-loop simulations with on-board software or for operator-in-the-loop simulations.
Sohl, G.↗
ROAMS: Rover Analysis, Modeling and Simulation Software
In this paper, we present the development of ROAMS software for real-time simulation of mobile robotic vehicles.
kinematics Mars-like terrain↗
Secure Roaming with 5G
This invited talk in the 2023 6th IEEE 5G Workshop on First Responder and Tactical Networks discusses security improvement introduced by the 3GPP standards to the 5G roaming capabilities over 4G/LTE (Long Term Evolution) standards.
5G↗
Thermochemistry of the smallest QOOH radical from the roaming fragmentation of energy selected methyl hydroperoxide ions
Here, the dissociative photoionization processes of methyl hydroperoxide (CH 3 OOH) have been studied by imaging Photoelectron Photoion Coincidence (iPEPICO) spectroscopy experiments as well as quantum-chemical and statistical rate calculations. Energy selected CH 3 OOH + ions dissociate into CH 2 OOH + , HCO + , CH 3 + , and H 3 O + ions in the 11.4–14.0 eV photon energy range. The lowest-energy dissociation channel is the formation of the cation of the smallest “QOOH” radical, CH 2 OOH + . An extended RRKM model fitted to the experimental data yields a 0 K appearance energy of 11.647 ± 0.005 eV for the CH 2 OOH + ion, and a 74.2 ± 2.6 kJ mol -1 mixed experimental-theoretical 0 K heat of formation for the CH 2 OOH radical. The proton affinity of the Criegee intermediate, CH 2 OO, was also obtained from the heat of formation of CH 2 OOH + (792.8 ± 0.9 kJ mol -1 ) to be 847.7 ± 1.1 kJ mol - 1, reducing the uncertainty of the previously available computational value by a factor of 4. RRKM modeling of the complex web of possible rearrangement-dissociation processes was used to model the higher-energy fragmentation. Supported by Born–Oppenheimer molecular dynamics simulations, we found that the HCO + fragment ion is produced through a roaming transition state followed by a low barrier. Lastly, H 3 O + is formed in a consecutive process from the CH 2 OOH + fragment ion, while direct C–O fission of the molecular ion leads to the methyl cation.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Photodissociation of methyl formate: Conical intersections, roaming and triple fragmentation
The photodissociation channels of methyl formate have been extensively investigated by two different advanced experimental techniques, ion imaging and Fourier-Transform-Infrared emission spectroscopy, combined with quantum chemical calculations and molecular dynamics simulations. Our aim is to characterize the role of alternative routes to the conventional transition-state mediated pathway: the roaming and the triple fragmentation processes. The photolysis experiments, carried out at a range of laser wavelengths in the vicinity of the triple fragmentation threshold, beside the simulation of large bunches of classical trajectories with different initial conditions, have shown that both mechanisms share a common path that involves a conical intersection during the relaxation process from the electronic excited state S{sub 1} to the ground state S{sub 0}.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Phase space barriers and dividing surfaces in the absence of critical points of the potential energy: Application to roaming in ozone
We examine the phase space structures that govern reaction dynamics in the absence of critical points on the potential energy surface. We show that in the vicinity of hyperbolic invariant tori, it is possible to define phase space dividing surfaces that are analogous to the dividing surfaces governing transition from reactants to products near a critical point of the potential energy surface. We investigate the problem of capture of an atom by a diatomic molecule and show that a normally hyperbolic invariant manifold exists at large atom-diatom distances, away from any critical points on the potential. This normally hyperbolic invariant manifold is the anchor for the construction of a dividing surface in phase space, which defines the outer or loose transition state governing capture dynamics. We present an algorithm for sampling an approximate capture dividing surface, and apply our methods to the recombination of the ozone molecule. We treat both 2 and 3 degrees of freedom models with zero total angular momentum. We have located the normally hyperbolic invariant manifold from which the orbiting (outer) transition state is constructed. This forms the basis for our analysis of trajectories for ozone in general, but with particular emphasis on the roaming trajectories.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Regional Oil and gas Aerial Methane Synthesis model (ROAMS) v2.0
The Regional Oil and gas Aerial Methane Synthesis model is a tool to convert the results of wide-area, source-resolved aerial methane remote sensing surveys of oil and natural gas infrastructure in a given region into methane emissions inventories (estimates of the magnitude and breakdown of methane emissions from the surveyed infrastructure). The tool leverages databases of source-resolved methane emissions detected in aerial surveys, aerial survey coverage information (which areas were measured and when), data summarizing surveyed oil and natural gas infrastructure and production (derived from third-party databases), as well as state-of-the-art mechanistic emissions simulation tools to characterize emissions too small for the aerial system to see. The regional methane emissions estimates produced by this tool are much more granular in both space and asset type than common satellite- or flux tower-based regional estimates. Unlike other tools for converting site-level measurements into regional emissions estimates, our unique geostatistical approach integrates aerially measured emissions with limited need for statistical extrapolation, which can be highly sensitive to modeler assumptions. As a result, ROAMS-based estimates of regional methane emissions from oil and gas activity are widely viewed as highly credible, as evidenced by the success of Dr. Sherwin's recent paper in Nature.
Sherwin, Evan [Lawrence Berkeley National Laborato↗
Regional Oil and gas Aerial Methane Synthesis model (Analytica) (ROAMS Analytica) v1.5.2
The Regional Oil and gas Aerial Methane Synthesis model (Analytica) is a tool to convert the results of wide-area, source-resolved aerial methane remote sensing surveys of oil and natural gas infrastructure in a given region into methane emissions inventories (estimates of the magnitude and breakdown of methane emissions from the surveyed infrastructure). This version is written in the Analytica programming language, and this version accompanies a correction in preparation for submission to Sherwin et al. 2024 (Nature). The tool leverages databases of source-resolved methane emissions detected in aerial surveys, aerial survey coverage information (which areas were measured and when), data summarizing surveyed oil and natural gas infrastructure and production (derived from third-party databases), as well as state-of-the-art mechanistic emissions simulation tools to characterize emissions too small for the aerial system to see. The regional methane emissions estimates produced by this tool are much more granular in both space and asset type than common satellite- or flux tower-based regional estimates. Unlike other tools for converting site-level measurements into regional emissions estimates, our unique geostatistical approach integrates aerially measured emissions with limited need for statistical extrapolation, which can be highly sensitive to modeler assumptions. As a result, ROAMS-based estimates of regional methane emissions from oil and gas activity are widely viewed as highly credible, as evidenced by the success of Dr. Sherwin's recent paper in Nature.
Sherwin, Evan [Lawrence Berkeley National Laborato↗
ROAMS: planetary surface rover simulation environment
This paper describes the ongoing development of the ROAMS physics-based simulator for planetary surface exploration rover vehicles.
rovers modeling simulation↗