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  • 1
    Electronic Resource
    Electronic Resource
    Collisional Quenching of OH Radio Emission from Comet Hale-Bopp (1997)
    Springer
    Earth, moon and planets 78 (1997), S. 45-51 
    Details
    ISSN: 1573-0794
    Keywords: Comets ; production rates ; OH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Observations of comets in the 18-cm OH transitions offer a means to probe gas production, kinematics, and OH excitation in comets. We present initial results of OH observations of comet Hale-Bopp obtained with the NRAO 43 m antenna located in Greenbank, WV. Maps of the emission provide strong constraints on the amount of quenching of the inversion of the OH ground state Λ-doublet in the coma. Analysis of the total radio OH flux and maps of its radial brightness distribution indicate a quenched region on the order of ∼500,000 km during March and April 1997. This large value is generally consistent with previous observations of radio OH quenching in lower production rate comets when the high production rate of comet Hale-Bopp is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006258908857
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  • 2
    Electronic Resource
    Electronic Resource
    The HNC/HCN Ratio in Comets (1997)
    Springer
    Earth, moon and planets 78 (1997), S. 29-35 
    Details
    ISSN: 1573-0794
    Keywords: Comets ; interstellar molecules
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The abundance ratio of the isomers HCN and HNC has been investigated in comet Hale-Bopp (C/1995 O1) through observations of the J = 4−3 rotational transitions of both species for heliocentric distances 0.93 〈 r 〈 3 AU, both pre- and post-perihelion. After correcting for the optical depth of the stronger HCN line, we find that the column density ratio of HNC/HCN in our telescope beam increases significantly as the comet approaches the Sun. We compare this behavior to that predicted from an ion-molecule chemical model and conclude that the HNC is produced insignificant measure by chemical processes in the coma; i.e., for comet Hale-Bopp, HNC is not a parent molecule sublimating from the nucleus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006202823878
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  • 3
    Electronic Resource
    Electronic Resource
    Hco+ in the Coma of Comet Hale–Bopp (1997)
    Springer
    Earth, moon and planets 77 (1997), S. 253-258 
    Details
    ISSN: 1573-0794
    Keywords: Comets ; HCO+ ; chemistry ; plasmas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Maps of comet C/1995 O1 (Hale-Bopp) in the millimeter-wave emission of the ion HCO+ revealed a local minimum near the nucleus position, with a maximum about 100,000 km in the antisolar direction. These observed features of the HCO+ emission require a low abundance of HCO+ due to enhanced destruction in the inner coma of the comet, within a region of low electron temperature (Te). To set constraints on the formation of HCO+ in the coma, as well as the location and magnitude of the transition to higher Te, the data are compared with the results of ion-molecule chemistry models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006285703521
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