Subrata Chakraborty | University of California, San Diego (original) (raw)

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Research paper thumbnail of Massive isotopic effect in vacuum UV photodissociation of N2 and implications for meteorite data

Nitrogen isotopic distributions in the solar system extend across an enormous range, from −400‰, ... more Nitrogen isotopic distributions in the solar system extend across an enormous range, from −400‰, in the solar wind and Jovian atmosphere, to about 5,000‰ in organic matter in carbonaceous chondrites. Distributions such as these require complex processing of nitrogen reservoirs and extraordinary isotope effects. While theoretical models invoke ion-neutral exchange reactions outside the protoplanetary disk and photochemical self-shielding on the disk surface to explain the variations, there are no experiments to substantiate these models. Experimental results of N2 photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched δ15N values from 648‰ to 13,412‰ in product NH3, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N2, plausibly explains the range of δ15N in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.

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Research paper thumbnail of Decadal Δ 17 O record of tropospheric CO 2 : Verification of a stratospheric component in the troposphere

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Research paper thumbnail of Mass-Independent Oxygen Isotopic Partitioning During Gas-Phase SiO2 Formation

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Research paper thumbnail of The Physical Chemistry of Mass-Independent Isotope Effects and Their Observation in Nature

Historically, the physical chemistry of isotope effects and precise measurements in samples from ... more Historically, the physical chemistry of isotope effects and precise measurements in samples from nature have provided information on processes that could not have been obtained otherwise. With the discovery of a mass-independent isotopic fractionation during the formation of ozone, a new physical chemical basis for isotope effects required development. Combined theoretical and experimental developments have broadened this understanding and extended the range of chemical systems where these unique effects occur. Simultaneously, the application of mass-independent isotopic measurements to an extensive range of both terrestrial and extraterrestrial systems has furthered the understanding of events such as solar system origin and evolution and planetary atmospheric chemistry, present and past.

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Research paper thumbnail of Isotopic fractionation of the O3-nitric oxide reaction

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Research paper thumbnail of Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge

Meteoritics & Planetary Science, 2007

Abstract— We report the first production of non-mass-dependently fractionated silicate smokes fro... more Abstract— We report the first production of non-mass-dependently fractionated silicate smokes from the gas phase at room temperature from a stream of silane and/or pentacarbonyl iron in a molecular hydrogen (or helium) flow mixed with molecular oxygen (or nitrous oxide). The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in 17O and 18O. The maximum Δ17O observed is + 4.7‰ for an iron oxide produced in flowing hydrogen, using O2 as the oxidant. More typical displacements are 1–2‰ above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation.

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Research paper thumbnail of Chemical and Isotopic Evolution of the Solar Nebula and Protoplanetary Disks

In this chapter we review recent advances in our understanding of the chemical and isotopic evolu... more In this chapter we review recent advances in our understanding of the chemical and isotopic evolution of protoplanetary disks and the solar nebula. Current observational and meteoritic constraints on physical conditions and chemical composition of gas and dust in these systems are presented. A variety of chemical and photochemical processes that occur in planet-forming zones and beyond, in both gas phase and on grain surfaces, are overviewed. The discussion is based upon radio-interferometric, meteoritic, space-born, and laboratory-based observations,measurements and theories. Linkage between cosmochemical and astrochemical data are presented, and interesting research puzzles are discussed.

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Research paper thumbnail of Mass-independent isotopic fractionation: Recent developments

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Research paper thumbnail of Oxygen isotopic fractionation during UV and visible light photodissociation of ozone

Chemical Physics, 2003

... The emitted photons were at wavelength range of 520±2 nm and 630±4 nm in two different subset... more ... The emitted photons were at wavelength range of 520±2 nm and 630±4 nm in two different subsets of the experiments. This irradiation was done for 60 to 1500 min to dissociate different fractions of ozone. ... Res. Lett. 29, 23-4 (2002). Electronic mail: bhatta@prl.ernet.in. ...

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Research paper thumbnail of Reply to ‘Comment on ‘Oxygen isotopic anomaly in surface induced ozone dissociation’

Chemical Physics Letters, 2003

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Research paper thumbnail of Corrigendum to: Oxygen isotopic anomaly in surface induced ozone dissociation

Chemical Physics Letters, 2003

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Research paper thumbnail of Oxygen isotopic anomaly in surface induced ozone dissociation

Chemical Physics Letters, 2003

The products of ozone dissociation occurring on glass surface are enriched in heavy oxygen isotop... more The products of ozone dissociation occurring on glass surface are enriched in heavy oxygen isotopes ( and ) in a mass independent () fashion. Such behavior is in contrast to the case of thermal dissociation where fractionation is mass dependent (). Even photo-dissociation by visible light is a mass dependent process. The mass independent fractionation in surface dissociation can probably be explained by assuming that the dissociation takes place via a short-lived complex involving the ozone molecule and an active surface site. The anomalous isotopic fractionation in surface dissociation can be useful to decipher the mechanism of surface reaction in some cases.

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Research paper thumbnail of Reply to comment by D. Krankowsky et al. on “Low-pressure dependency of the isotopic enrichment in ozone: Stratospheric implications” by S. K. Bhattacharya et al

Journal of Geophysical Research, 2003

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Research paper thumbnail of Experimental investigation of oxygen isotope exchange between CO2 and O(1D) and its relevance to the stratosphere

Journal of Geophysical Research, 2003

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Research paper thumbnail of Low-pressure dependency of the isotopic enrichment in ozone: Stratospheric implications

Journal of Geophysical Research, 2002

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Research paper thumbnail of Response to Comments on ``Experimental Test of Self-Shielding in Vacuum Ultraviolet Photodissociation of CO

Science, 2009

We address the comments by Lyons et al., Federman and Young, and Yin et al. regarding the interpr... more We address the comments by Lyons et al., Federman and Young, and Yin et al. regarding the interpretation of our carbon monoxide photodissociation experiments and provide further experimental data analysis, including measured synchrotron beam profiles. The experimental data do not support existing self-shielding models that attempt to explain observed meteoritic oxygen isotopic compositions because they rely on previously untested theoretical assumptions.

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Research paper thumbnail of Experimental Test of Self-Shielding in Vacuum Ultraviolet Photodissociation of CO

Science, 2008

Self-shielding of carbon monoxide (CO) within the nebular disk has been proposed as the source of... more Self-shielding of carbon monoxide (CO) within the nebular disk has been proposed as the source of isotopically anomalous oxygen in the solar reservoir and the source of meteoritic oxygen isotopic compositions. A series of CO photodissociation experiments at the Advanced Light Source show that vacuum ultraviolet (VUV) photodissociation of CO produces large wavelength-dependent isotopic fractionation. An anomalously enriched atomic oxygen reservoir can thus be generated through CO photodissociation without self-shielding. In the presence of optical self-shielding of VUV light, the fractionation associated with CO dissociation dominates over self-shielding. These results indicate the potential role of photochemistry in early solar system formation and may help in the understanding of oxygen isotopic variations in Genesis solar-wind samples.

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Research paper thumbnail of Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: wavelength, pressure, and temperature dependency

The Journal of chemical physics, 2012

Several absorption bands exist in the vacuum ultraviolet (VUV) region of carbon monoxide (CO). Em... more Several absorption bands exist in the vacuum ultraviolet (VUV) region of carbon monoxide (CO). Emission spectra indicate that these bands are all predissociative. Experimental results of CO photodissociation by vacuum ultraviolet photons (90 to 108 nm; ∼13 to 11 eV) from the Advanced Light Source synchrotron by measurement of the oxygen isotopic composition of the products are presented here. A large (few hundred per mil) range of oxygen isotopic compositions are observed in the CO photodissociation product and are wavelength dependent. Slope values (δ('17)O/δ('18)O) ranging from 0.72 to 1.36 were observed in the oxygen three-isotope space (δ('18)O vs. δ('17)O), which anti-correlated with increasing synchrotron photon energy, and indicates a dependency on the upper electronic state specific dissociation dynamics (e.g., perturbation and coupling associated with a particular state). An unprecedented magnitude in isotope fractionation was observed for photodissociation at 105 and 107 nm and is found to be associated with accidental predissociation of the vibrational states (ν = 0 and 1) for the upper electronic state E(1)Π. A significant temperature dependency in oxygen isotopic fractionation was observed, indicating a rotational level dependency in the predissociation process.

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Research paper thumbnail of Sulfur isotopic fractionation in vacuum UV photodissociation of hydrogen sulfide and its potential relevance to meteorite analysis

Proceedings of the National Academy of Sciences of the United States of America, 2013

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Research paper thumbnail of Massive isotopic effect in vacuum UV photodissociation of N2 and implications for meteorite data

Nitrogen isotopic distributions in the solar system extend across an enormous range, from −400‰, ... more Nitrogen isotopic distributions in the solar system extend across an enormous range, from −400‰, in the solar wind and Jovian atmosphere, to about 5,000‰ in organic matter in carbonaceous chondrites. Distributions such as these require complex processing of nitrogen reservoirs and extraordinary isotope effects. While theoretical models invoke ion-neutral exchange reactions outside the protoplanetary disk and photochemical self-shielding on the disk surface to explain the variations, there are no experiments to substantiate these models. Experimental results of N2 photolysis at vacuum UV wavelengths in the presence of hydrogen are presented here, which show a wide range of enriched δ15N values from 648‰ to 13,412‰ in product NH3, depending upon photodissociation wavelength. The measured enrichment range in photodissociation of N2, plausibly explains the range of δ15N in extraterrestrial materials. This study suggests the importance of photochemical processing of the nitrogen reservoirs within the solar nebula.

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Research paper thumbnail of Decadal Δ 17 O record of tropospheric CO 2 : Verification of a stratospheric component in the troposphere

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Research paper thumbnail of Mass-Independent Oxygen Isotopic Partitioning During Gas-Phase SiO2 Formation

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Research paper thumbnail of The Physical Chemistry of Mass-Independent Isotope Effects and Their Observation in Nature

Historically, the physical chemistry of isotope effects and precise measurements in samples from ... more Historically, the physical chemistry of isotope effects and precise measurements in samples from nature have provided information on processes that could not have been obtained otherwise. With the discovery of a mass-independent isotopic fractionation during the formation of ozone, a new physical chemical basis for isotope effects required development. Combined theoretical and experimental developments have broadened this understanding and extended the range of chemical systems where these unique effects occur. Simultaneously, the application of mass-independent isotopic measurements to an extensive range of both terrestrial and extraterrestrial systems has furthered the understanding of events such as solar system origin and evolution and planetary atmospheric chemistry, present and past.

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Research paper thumbnail of Isotopic fractionation of the O3-nitric oxide reaction

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Research paper thumbnail of Non-mass-dependent oxygen isotopic fractionation in smokes produced in an electrical discharge

Meteoritics & Planetary Science, 2007

Abstract— We report the first production of non-mass-dependently fractionated silicate smokes fro... more Abstract— We report the first production of non-mass-dependently fractionated silicate smokes from the gas phase at room temperature from a stream of silane and/or pentacarbonyl iron in a molecular hydrogen (or helium) flow mixed with molecular oxygen (or nitrous oxide). The smokes were formed at the Goddard Space Flight Center (GSFC) at total pressures of just under 100 Torr in an electrical discharge powered by a Tesla coil, were collected from the surfaces of the copper electrodes after each experiment and sent to the University of California at San Diego (UCSD) for oxygen isotopic analysis. Transmission electron microscopy studies of the smokes show that they grew in the gas phase rather than on the surfaces of the electrodes. We hypothesize at least two types of fractionation processes occurred during formation of the solids: a mass-dependent process that made isotopically lighter oxides compared to our initial oxygen gas composition followed by a mass-independent process that produced oxides enriched in 17O and 18O. The maximum Δ17O observed is + 4.7‰ for an iron oxide produced in flowing hydrogen, using O2 as the oxidant. More typical displacements are 1–2‰ above the equilibrium fractionation line. The chemical reaction mechanisms that yield these smokes are still under investigation.

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Research paper thumbnail of Chemical and Isotopic Evolution of the Solar Nebula and Protoplanetary Disks

In this chapter we review recent advances in our understanding of the chemical and isotopic evolu... more In this chapter we review recent advances in our understanding of the chemical and isotopic evolution of protoplanetary disks and the solar nebula. Current observational and meteoritic constraints on physical conditions and chemical composition of gas and dust in these systems are presented. A variety of chemical and photochemical processes that occur in planet-forming zones and beyond, in both gas phase and on grain surfaces, are overviewed. The discussion is based upon radio-interferometric, meteoritic, space-born, and laboratory-based observations,measurements and theories. Linkage between cosmochemical and astrochemical data are presented, and interesting research puzzles are discussed.

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Research paper thumbnail of Mass-independent isotopic fractionation: Recent developments

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Research paper thumbnail of Oxygen isotopic fractionation during UV and visible light photodissociation of ozone

Chemical Physics, 2003

... The emitted photons were at wavelength range of 520±2 nm and 630±4 nm in two different subset... more ... The emitted photons were at wavelength range of 520±2 nm and 630±4 nm in two different subsets of the experiments. This irradiation was done for 60 to 1500 min to dissociate different fractions of ozone. ... Res. Lett. 29, 23-4 (2002). Electronic mail: bhatta@prl.ernet.in. ...

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Research paper thumbnail of Reply to ‘Comment on ‘Oxygen isotopic anomaly in surface induced ozone dissociation’

Chemical Physics Letters, 2003

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Research paper thumbnail of Corrigendum to: Oxygen isotopic anomaly in surface induced ozone dissociation

Chemical Physics Letters, 2003

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Research paper thumbnail of Oxygen isotopic anomaly in surface induced ozone dissociation

Chemical Physics Letters, 2003

The products of ozone dissociation occurring on glass surface are enriched in heavy oxygen isotop... more The products of ozone dissociation occurring on glass surface are enriched in heavy oxygen isotopes ( and ) in a mass independent () fashion. Such behavior is in contrast to the case of thermal dissociation where fractionation is mass dependent (). Even photo-dissociation by visible light is a mass dependent process. The mass independent fractionation in surface dissociation can probably be explained by assuming that the dissociation takes place via a short-lived complex involving the ozone molecule and an active surface site. The anomalous isotopic fractionation in surface dissociation can be useful to decipher the mechanism of surface reaction in some cases.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Reply to comment by D. Krankowsky et al. on “Low-pressure dependency of the isotopic enrichment in ozone: Stratospheric implications” by S. K. Bhattacharya et al

Journal of Geophysical Research, 2003

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Research paper thumbnail of Experimental investigation of oxygen isotope exchange between CO2 and O(1D) and its relevance to the stratosphere

Journal of Geophysical Research, 2003

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Research paper thumbnail of Low-pressure dependency of the isotopic enrichment in ozone: Stratospheric implications

Journal of Geophysical Research, 2002

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Research paper thumbnail of Response to Comments on ``Experimental Test of Self-Shielding in Vacuum Ultraviolet Photodissociation of CO

Science, 2009

We address the comments by Lyons et al., Federman and Young, and Yin et al. regarding the interpr... more We address the comments by Lyons et al., Federman and Young, and Yin et al. regarding the interpretation of our carbon monoxide photodissociation experiments and provide further experimental data analysis, including measured synchrotron beam profiles. The experimental data do not support existing self-shielding models that attempt to explain observed meteoritic oxygen isotopic compositions because they rely on previously untested theoretical assumptions.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Experimental Test of Self-Shielding in Vacuum Ultraviolet Photodissociation of CO

Science, 2008

Self-shielding of carbon monoxide (CO) within the nebular disk has been proposed as the source of... more Self-shielding of carbon monoxide (CO) within the nebular disk has been proposed as the source of isotopically anomalous oxygen in the solar reservoir and the source of meteoritic oxygen isotopic compositions. A series of CO photodissociation experiments at the Advanced Light Source show that vacuum ultraviolet (VUV) photodissociation of CO produces large wavelength-dependent isotopic fractionation. An anomalously enriched atomic oxygen reservoir can thus be generated through CO photodissociation without self-shielding. In the presence of optical self-shielding of VUV light, the fractionation associated with CO dissociation dominates over self-shielding. These results indicate the potential role of photochemistry in early solar system formation and may help in the understanding of oxygen isotopic variations in Genesis solar-wind samples.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Oxygen isotope fractionation in the vacuum ultraviolet photodissociation of carbon monoxide: wavelength, pressure, and temperature dependency

The Journal of chemical physics, 2012

Several absorption bands exist in the vacuum ultraviolet (VUV) region of carbon monoxide (CO). Em... more Several absorption bands exist in the vacuum ultraviolet (VUV) region of carbon monoxide (CO). Emission spectra indicate that these bands are all predissociative. Experimental results of CO photodissociation by vacuum ultraviolet photons (90 to 108 nm; ∼13 to 11 eV) from the Advanced Light Source synchrotron by measurement of the oxygen isotopic composition of the products are presented here. A large (few hundred per mil) range of oxygen isotopic compositions are observed in the CO photodissociation product and are wavelength dependent. Slope values (δ('17)O/δ('18)O) ranging from 0.72 to 1.36 were observed in the oxygen three-isotope space (δ('18)O vs. δ('17)O), which anti-correlated with increasing synchrotron photon energy, and indicates a dependency on the upper electronic state specific dissociation dynamics (e.g., perturbation and coupling associated with a particular state). An unprecedented magnitude in isotope fractionation was observed for photodissociation at 105 and 107 nm and is found to be associated with accidental predissociation of the vibrational states (ν = 0 and 1) for the upper electronic state E(1)Π. A significant temperature dependency in oxygen isotopic fractionation was observed, indicating a rotational level dependency in the predissociation process.

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Research paper thumbnail of Sulfur isotopic fractionation in vacuum UV photodissociation of hydrogen sulfide and its potential relevance to meteorite analysis

Proceedings of the National Academy of Sciences of the United States of America, 2013

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