Linewidths of the Rotational Spectra of Symmetric‐Top Molecules

Measurements of linewidths are reported for some 50 rotational transitions (J→J + 1) of the CH335Cl, CH337Cl, CH379Br, CH381Br, CH3I, CH3CN, and CH3CCH molecules. The CH3CN molecule has exceptionally wide lines (100 Mc/sec·torr) due to the large dipole moment (3.92 D). The experimental data are compared with the theoretical widths which are calculated using the Anderson theory with dipole–dipole interaction. With the exception of the CH3CCH molecule, the theoretical widths are larger than the experimental ones. The over‐all agreement between theory and experiment is within 30%.