When laboratory study of some molecule is not available, one may plan to use data obtained from Quantum Chemistry software, such as GAUSSIAN, MOLPRO, NWCHEM, etc. For our investigation of cosmic molecules, we need reliable data for rotational and centrifugal distortion constants. For some molecules, we have obtained these data with the help of Quantum Chemistry software GAUSSIAN and compared them with those obtained from the laboratory studies. We have found that in some cases, the two sets of

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... ata are very close to each other whereas in some cases, they differ very much. As the laboratory measurements provide the most reliable data, one