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Silicon ions below 100 km: A case for SiO 2 +
Author(s) -
Goldberg Richard A.
Publication year - 1975
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs010i003p00329
Subject(s) - ion , silicon , materials science , metal , analytical chemistry (journal) , atomic physics , physics , chemistry , metallurgy , quantum mechanics , chromatography
Silicon ions are normally detected at altitudes above 100 km and within sporadic‐ E layers. Traces have rarely been observed within the more permanent metallic layer near 93 km. This is surprising since silicon is an important constituent of chondritic meteorites, which ablate material in this region to provide a primary source of the metallic species observed there. In this work, we present evidence that Si + ions form SiO 2 + at the lower altitudes, and exist in this ionic state prior to recombination. A rocket launched from El Arenosillo, Spain, on 3 July 1972, at 0743 LMT (χ = 57.1°), during the predicted period of the β Taurids meteor shower, passed through a continuous belt of metallic ions that began near 85 km, ended near 115 km, and exhibited an order of magnitude increase in the form of a layer near 114 km. Si + was measured in and below the ledge down to 103 km. It showed a rapid decrease below this height. A comparison of the isotopic ratio for nickel, [ 60 Ni]/[ 58 Ni], with the measured ions shows too large a ratio for the ions below 100 km, suggesting contribution to 60 + from other sources. A prime candidate is SiO 2 + , since Si + is observed to decrease in the region where the ratio becomes too large. No evidence for SiO + (44 + ) is present in the data, indicating that Si + forms SiO 2 + either directly or through SiO + in a short‐lived state. Radiative association is offered as a primary mechanism for SiO 2 + production and yields a calculated reaction rate of 2×10 −16 cm 3 sec −1 .