Abstract
Existing galactic plane CO surveys are able to detect molecular clouds which contain substantial CO with an excitation temperature > or approx. =5 K. We have tested the possibility that substantial numbers of molecular clouds exist where T/sub ex/< or approx. =5 K. CO observations were obtained in the direction of 17 continuum sources which showed multiple H/sub 2/CO absorption features at a wavelength of 6 cm. The H/sub 2/CO features were taken as evidence of a molecular cloud, and CO observations were used to determine T/sub ex/ of that cloud. Although a few clouds may have T/sub ex/ slightly less than 5 K, a large amount of mass does not appear to be hidden in such ultracold molecular clouds with detectable H/sub 2/CO absorption.
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