Knowledge Bank

Collision-induced transitions have been investigated among astronomically-interesting rotational energy levels of $CH3OH$ in the presence of the foreign gases He had $H2$. The conclusion of Lees and $Oka1$ that $\Delta K=0$ collisional transitions are preferred over $\Delta K=\pm 1$ transitions is substantiated, however collisional transfer via $\Delta K=\pm 1$ transitions has been observed between the levels of the $4-1\leftarrow 30$ E transition at 36169 MHz detected in $SgrB22$ and those of the $52\leftarrow 51$ E transition at 24959 MHz detected in Ori A. The implications of the results for the excitation of interstellar methanol are discussed. $\mathrm{<mrow\; data-mjx-texclass="ORD">1</mrow>}$ R. M. Lees and T. Oka, J. Chem. Phys. 51, 3027 (1969). $\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ B. E. Turner, M.A. Gordon and G. T. Wrixon, Ap. J. 177, 609 (1972). $\mathrm{<mrow\; data-mjx-texclass="ORD">3</mrow>}$ A. H. Barrett, P. R. Schwartz and J. W. Waters, Ap. J. 168, L101 (1971).