ORCID Profile
0000-0003-1216-673X
Current Organisation
E O Lawrence Berkeley National Laboratory
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Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D3SC00911D
Abstract: The gas-phase preparation of naphthalene (C 10 H 8 ) molecule has been revealed through an isomer selective product detection via the reaction of the resonantly stabilized benzyl and the propargyl radicals.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP02042G
Abstract: Electronic excitation and concomitant energy transfer leading to Penning ionization in argon–acetylene clusters are investigated with synchrotron-based photoionization mass spectrometry and electronic structure calculations.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP02216K
Abstract: 1 H -Phenalene can be synthesized via the reaction of the 1-naphthyl radical with methylacetylene and allene under high temperature conditions prevalent in carbon-rich circumstellar environments and combustion systems.
Publisher: American Chemical Society (ACS)
Date: 26-01-2023
DOI: 10.1021/JACS.2C12045
Publisher: Springer Science and Business Media LLC
Date: 15-08-2019
DOI: 10.1038/S41467-019-11652-5
Abstract: Polycyclic aromatic hydrocarbons (PAHs) represent key molecular building blocks leading to carbonaceous nanoparticles identified in combustion systems and extraterrestrial environments. However, the understanding of their formation and growth in these high temperature environments has remained elusive. We present a mechanism through laboratory experiments and computations revealing how the prototype PAH—naphthalene—can be efficiently formed via a rapid 1-indenyl radical—methyl radical reaction. This versatile route converts five- to six-membered rings and provides a detailed view of high temperature mass growth processes that can eventually lead to graphene-type PAHs and two-dimensional nanostructures providing a radical new view about the transformations of carbon in our universe.
Publisher: American Chemical Society (ACS)
Date: 04-06-2021
Publisher: American Chemical Society (ACS)
Date: 07-03-2022
Abstract: Polyol-water clusters provide a template to probe ionization and solvation processes of paramount interest in atmospheric and interstellar chemistry. We generate glycerol water clusters in a continuous supersonic jet expansion and interrogate the neutral species with synchrotron-based tunable vacuum ultraviolet photoionization mass spectrometry. A series of glycerol fragments (
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0CP06537D
Abstract: Corannulene can be formed through molecular mass growth processes in circumstellar envelopes.
Publisher: Wiley
Date: 11-05-2020
Publisher: Elsevier BV
Date: 08-2022
Publisher: Springer Science and Business Media LLC
Date: 03-04-2019
DOI: 10.1038/S41467-019-09224-8
Abstract: A synthetic route to racemic helicenes via a vinylacetylene mediated gas phase chemistry involving elementary reactions with aryl radicals is presented. In contrast to traditional synthetic routes involving solution chemistry and ionic reaction intermediates, the gas phase synthesis involves a targeted ring annulation involving free radical intermediates. Exploiting the simplest helicene as a benchmark, we show that the gas phase reaction of the 4-phenanthrenyl radical ([C 14 H 9 ] • ) with vinylacetylene (C 4 H 4 ) yields [4]-helicene (C 18 H 12 ) along with atomic hydrogen via a low-barrier mechanism through a resonance-stabilized free radical intermediate (C 18 H 13 ). This pathway may represent a versatile mechanism to build up even more complex polycyclic aromatic hydrocarbons such as [5]- and [6]-helicene via stepwise ring annulation through bimolecular gas phase reactions in circumstellar envelopes of carbon-rich stars, whereas secondary reactions involving hydrogen atom assisted isomerization of thermodynamically less stable isomers of [4]-helicene might be important in combustion flames as well.
Publisher: Wiley
Date: 16-10-2019
Abstract: Polycyclic aromatic hydrocarbons (PAHs) represent the link between resonance-stabilized free radicals and carbonaceous nanoparticles generated in incomplete combustion processes and in circumstellar envelopes of carbon rich asymptotic giant branch (AGB) stars. Although these PAHs resemble building blocks of complex carbonaceous nanostructures, their fundamental formation mechanisms have remained elusive. By exploring these reaction mechanisms of the phenyl radical with biphenyl/naphthalene theoretically and experimentally, we provide compelling evidence on a novel phenyl-addition/dehydrocyclization (PAC) pathway leading to prototype PAHs: triphenylene and fluoranthene. PAC operates efficiently at high temperatures leading through rapid molecular mass growth processes to complex aromatic structures, which are difficult to synthesize by traditional pathways such as hydrogen-abstraction/acetylene-addition. The elucidation of the fundamental reactions leading to PAHs is necessary to facilitate an understanding of the origin and evolution of the molecular universe and of carbon in our galaxy.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1CP02169A
Abstract: Quinoline and isoquinoline can be formed through molecular mass growth processes in low-temperature environments.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0CP03846F
Abstract: The reaction of indenyl radicals with vinylacetylene leads to cyclopentanaphthalene at low temperature.
Publisher: AIP Publishing
Date: 19-10-2018
DOI: 10.1063/1.5046521
Abstract: New photoresists are needed to advance extreme ultraviolet (EUV) lithography. The tailored design of efficient photoresists is enabled by a fundamental understanding of EUV induced chemistry. Processes that occur in the resist film after absorption of an EUV photon are discussed, and a new approach to study these processes on a fundamental level is described. The processes of photoabsorption, electron emission, and molecular fragmentation were studied experimentally in the gas-phase on analogs of the monomer units employed in chemically lified EUV resists. To demonstrate the dependence of the EUV absorption cross section on selective light harvesting substituents, halogenated methylphenols were characterized employing the following techniques. Photoelectron spectroscopy was utilized to investigate kinetic energies and yield of electrons emitted by a molecule. The emission of Auger electrons was detected following photoionization in the case of iodo-methylphenol. Mass-spectrometry was used to deduce the molecular fragmentation pathways following electron emission and atomic relaxation. To gain insight on the interaction of emitted electrons with neutral molecules in a condensed film, the fragmentation pattern of neutral gas-phase molecules, interacting with an electron beam, was studied and observed to be similar to EUV photon fragmentation. Below the ionization threshold, electrons were confirmed to dissociate iodo-methylphenol by resonant electron attachment.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP04375K
Abstract: Nucleation and crystallization arising from liquid to solid phase are involved in a multitude of processes in fields ranging from materials science to biology. Controlling the thermodynamics and kinetics of growth is advantageous to help tune the formation of complex morphologies. Here, we harness wide-angle X-ray scattering and vibrational spectroscopy to elucidate the mechanism for crystallization and growth of the metal-organic framework Co-MOF-74 within microscopic volumes enclosed in a capillary and an attenuated total reflection microchip reactor. The experiments reveal molecular and structural details of the growth processes, while the results of plane wave density functional calculations allow identification of lattice and linker modes in the formed crystals. Synthesis of the metal-organic framework with microscopic volumes leads to monodisperse and micron-sized crystals, in contrast to those typically observed under bulk reaction conditions. Reduction in the volume of reagents within the microchip reactor was found to accelerate the reaction rate. The coupling of spectroscopy with scattering to probe reactions in microscopic volumes promises to be a useful tool in the synthetic chemist's kit to understand chemical bonding and has potential in designing complex materials.
Publisher: American Chemical Society (ACS)
Date: 27-10-2020
Publisher: American Chemical Society (ACS)
Date: 30-12-2022
DOI: 10.1021/ACS.JPCLETT.1C03733
Abstract: Resonantly stabilized free radicals (RSFRs) have been contemplated as fundamental molecular building blocks and reactive intermediates in molecular mass growth processes leading to polycyclic aromatic hydrocarbons (PAHs) and carbonaceous nanoparticles on Earth and in deep space. By combining molecular beams and computational fluid dynamics simulations, we provide compelling evidence on the formation of benzene via the cyclopentadienyl-methyl reaction and of naphthalene through the cyclopentadienyl self-reaction, respectively. These systems offer benchmarks for the conversion of a five-membered ring to the 6π-aromatic (benzene) and the generation of the simplest 10π-PAH (naphthalene) at elevated temperatures. These results uncover molecular mass growth processes from the "bottom up" via RSFRs in high temperature circumstellar environments and combustion systems expanding our fundamental knowledge of the organic, hydrocarbon chemistry in our universe.
Publisher: American Chemical Society (ACS)
Date: 13-07-2023
Publisher: Springer Science and Business Media LLC
Date: 10-02-2022
DOI: 10.1038/S41467-022-28466-7
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are prevalent in deep space and on Earth as products in combustion processes bearing direct relevance to energy efficiency and environmental remediation. Reactions between hydrocarbon radicals in particular have been invoked as critical molecular mass growth processes toward cyclization leading to these PAHs. However, the mechanism of the formation of PAHs through radical – radical reactions are largely elusive. Here, we report on a combined computational and experimental study of the benzyl (C 7 H 7 ) radical self-reaction to phenanthrene and anthracene (C 14 H 10 ) through unconventional, isomer-selective excited state dynamics. Whereas phenanthrene formation is initiated via a barrierless recombination of two benzyl radicals on the singlet ground state surface, formation of anthracene commences through an exotic transition state on the excited state triplet surface through cycloaddition. Our findings challenge conventional wisdom that PAH formation via radical-radical reactions solely operates on electronic ground state surfaces and open up a previously overlooked avenue for a more “rapid” synthesis of aromatic, multi-ringed structures via excited state dynamics in the gas phase.
Publisher: Wiley
Date: 11-05-2020
Publisher: Wiley
Date: 16-10-2019
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2CP03084E
Abstract: Racemic mixtures of [5] and [6]helicenes can form in the gas-phase of the interstellar medium at ultralow temperatures in the absence of reaction barriers via molecular mass growth processes.
Publisher: American Chemical Society (ACS)
Date: 09-10-2023
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9CP02930C
Abstract: The three-ring polycyclic aromatic hydrocarbons (PAHs) 3H-benz[e]indene (C
Publisher: American Association for the Advancement of Science (AAAS)
Date: 08-09-2023
Location: United States of America
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for musahid ahmed.