Chemistry of barium released at high altitudes

Rosenberg, N. W.; Best, G. T.

doi:10.1021/j100680a009

Cited by 26 publications

(4 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Initially, we qualitatively compared number density predictions for four models with the unknown rate coefficients for DR and PI set at two limits of uncertainty. For DR, the limits were, 10 −8 exp(−927/T) and 10 −11 exp(−927/T) (with T in K) and for PI we set the limits at 0.001 and 0.03 s −1 , the latter being the high barium solar photoionization rate which has been demonstrated to involve a mechanism via a metastable state [ Rosenberg and Best , ]. The results clearly pointed to the need for a Sm replenishment mechanism, which in the present work is given by a substantial DR rate coefficient as postulated by Cox et al [].…”

Section: Observations and Modelingsupporting

confidence: 57%

A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases

et al. 2017

View full text Add to dashboard Cite

Two rocket‐borne releases of samarium vapor in the upper atmosphere occurred in May 2013, as part of the Metal Oxide Space Clouds experiment. The releases were characterized by a combination of optical and RF diagnostic instruments located at the Roi‐Namur launch site and surrounding islands and atolls. The evolution of the optical spectrum of the solar‐illuminated cloud was recorded with a spectrograph covering a 400–800 nm spectral range. The spectra exhibit two distinct spectral regions centered at 496 and 636 nm within which the relative intensities change insignificantly. The ratio between the integrated intensities within these regions, however, changes with time, suggesting that they are associated with different species. With the help of an equilibrium plasma spectral model we attribute the region centered at 496 nm to neutral samarium atoms (Sm I radiance) and features peaking at 649 nm to a molecular species. No evidence for structure due to Sm+ (Sm II) is identified. The persistence of the Sm I radiance suggests a high dissociative recombination rate for the chemi‐ionization product, SmO+. A one‐dimensional plasma chemical kinetic model of the evolution of the density ratio NSmO/NSm(t) demonstrates that the molecular feature peaking at 649 nm can be attributed to SmO radiance. SmO+ radiance is not identified. By adjusting the Sm vapor mass of the chemical kinetic model input to match the evolution of the total electron density determined by ionosonde data, we conclude that less than 5% of the payload samarium was vaporized.

show abstract

Section: Observations and Modelingsupporting

confidence: 57%

A combined spectroscopic and plasma chemical kinetic analysis of ionospheric samarium releases

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The chemistry of the releases is not extensive, but is included for completeness. , Barium and the other metal species are vaporized by highly exothermic thermite reactions such as Ba + CuO → Cu + BaO or Ti + 2B → TiB 2 . The active metal is mixed with the powdered thermite reactants in canisters onboard rocket or satellite payloads.…”

Section: Active Chemical Release Experimentsmentioning

confidence: 99%

Ambient and Modified Atmospheric Ion Chemistry: From Top to Bottom

2015

View full text Add to dashboard Cite

CONTENTS 1. Introduction 4542 1.1. Historical Overview and Goals 4542 1.2. Background Basics of the Atmosphere 4543 2. The Exosphere 4545 3. Thermosphere 4546 3.1. Composition and Positive Ion Chemistry 4546 3.2. Ion−Molecule Reactions 4547 3.2.1. O 2 + Reactions 4547 3.2.2. O + Reactions 4548 3.2.3. N + Reactions 4550 3.2.4. N 2 + Reactions 4550 3.3. Airglow and Dissociative Recombination 4551 4. Mesosphere 4552 4.1. Positive Ion Composition and Chemistry 4552 4.2. Negative Ion Composition and Chemistry 4554 4.3. Mutual Neutralization 4555 4.4. Meteoric Smoke 4555 5. Stratosphere and Troposphere 4556 5.1. Acid−Base Chemistry 4556 5.2. Ion-Induced (Mediated) Nucleation 4558 6. Active Chemical Release Experiments 4559 6.1. Background and Historical Perspective 4559 6.2. Atmospheric Tracer Experiments 4559 6.3. Plasma Enhancement Releases − Samarium Chemi-ionization 4560 6.4. Plasma Depletion Experiments − Ionospheric Holes 4561 6.5. Plasma Depletion Experiments − Electron Holes 4562 7. Summary and Conclusions 4564 Author Information 4565 Corresponding Author 4565 Notes 4565 Biographies 4565 Acknowledgments 4566 References 4566

show abstract

“…Chemical release experiments use barium due to its fast photoionization timescale of around 30 s. However, barium in chemical releases is not photoionized directly from the ground state. In fact, the photoioniztion time of barium from the ground state is hundreds of seconds (Rosenberg & Best, 1971). To include the photoionization of barium in the DSMC simulations, as well as the optical emission to be observed from the ground, we must model the excited states of barium neutrals and barium ions.…”

Section: Photoionization Of Barium Via Metastable Statesmentioning

confidence: 99%