LABORATORY MEASUREMENTS OF THE ABUNDANCE RATIO $[HCO^{+}]/[HOC^{+}]$ AND THEIR ASTROPHYSICAL IMPLICATIONS

$^{1}$ T.Nakanaga and T.Amano, Paper FA15, 41st Symposium on Molecular Spectroscopy and J. Mol. Spectrosc, to be published.Author Institution: Herzberg Institute of Astrophysics, National Research Council of Canada; Herzberg Institute of Astrophysics, National Laboratory for Chemical IndustryRecently the $\nu_{1}$ fundamental band of $HOC^{+}$ was observed in a hollow cathode discharge through a mixture of CO and $H_{2}.{^{1}}$ The reaction condition is quite a constrast to that used in previous microwave observations in which a large amount of Ar is needed as a buffer gas. The relative intensity of the infrared absorption lines of $HCO^{+}$ and $HOC^{+}$ was measured as a function of the pressures of $H_{2}$ and CO. In the laboratory conditions, the isomerization of $HOC^{+}$ to $HCO^{+}$ by CO was found to be a dominant depletion process of $HOC^{+}$. The abundnace ratio [$HCO^{+}]/[HOC^{+}$] was obtained to be about 220 under the most favorable reaction conditions for production of $HOC^{+}$. Although the rate constant of the catalytic isomerization of $HOC^{+}$ by $H_{2}$ is smaller than that of the isomerization reaction by CO by about an order of magnitude, the catalytic isomerization by $H_{2}$ may be the main depletion process of $HOC^{+}$ in dense dark clouds. The estimated rate constants derived in the present work gives an estimated abundance ratio [$HCO^{+}]/[HOC^{+}$] to be of the order of $10^{5}$ in dense dark clouds