MILLIMETER AND SUBMILLIMETER SPECTROSCOPY OF CCH, $CO^{+}, {HN_{2}}^{+}, HCO^{+ \ast}$

$^{*}$Supported by NASA, Grant NAGW-189. $^{1}$K.D. Tucker, M.L. Kutner, and P. Thaddeus, Ap. J. Let. 193, L115 (1974). $^{2}$K.V.L.N. Sastry, P. Helminger, A. Charo, E. Herbst, and F.C. De Lucia, Ap. J. Let. 251, L119 (1981).We have observed a number of transitions of the short-lived radical CCH as well as the molecular ions $CO^{+}, {HN_{2}}^{+}$, and $HCO^{+}$ by means of millimeter and submillimeter wave spectroscopic techniques. Accurate spectroscopic parameters have been calculated from these data. CCH was first identified in the gas phase by Tucker, Kutner, and $Thaddeus^{1}$ using radioastronomical techniques. Our work represents the first $reported^{2}$ microwave spectroscopic detection of this species. For the detection of CCH and other elusive laboratory species, we find the spectral region around 300 GHz to be optimum