THE MILLIMETER AND SUBMILLIMETER SPECTRUM OF ALCH3 (X(1)A(1))

The pure rotational spectrum of AlCH3 has been recorded using millimet er/submillimeter direct absorption techniques. This is the first time this species has been observed in the laboratory by any spectroscopic method. AlCH3 was created in a d.c. discharge by the reaction of alumi num vapor and dimethyl mercury. The K = 0, 1, 2, and 3 components in f ourteen rotational transitions of this symmetric top molecule were mea sured in the frequency range 188-517 GHz and several lines recorded fo r K = 4, 5 and 6 ladders as well. From these data, rotational paramete rs have been accurately determined. This study confirms the structure predicted for AlCH3 from theoretical calculations, as well as provides precise rest frequencies. Aluminum-bearing molecules have been observ ed in the late-type carbon star IRC + 10216, which also has a large ab undance of CH4. Hence, AlCH3 may be detectable in this object and perh aps in other sources.