Knowledge Bank

The first derivatives of the electric dipole moments along the symmetry coordinates were computed for $PH3$, $PD3$, $CH3F$, $C3F$, $CH3CL$, $CD3Cl$, $CH4$,$CD4$,$CH3D$,$CHD3$ AND $CH2$$D2$ by means of the deMon density functional program [A. St. Amant and D.R. Salahub, Chem. phys. Letters 169, 387-392 (1990)]. The absolute intensities of 220 vibration-rotational spectral lines of transitions to the vibrational states $\nu 2=1$ and $v5=1$ of $\mathrm{<mrow\; data-mjx-texclass="ORD">12</mrow>}CH3F$ were measured with a diode laser. The eigenvectors of the rovibrational states of $CH3F$ strongly perturbed by the x- y Coriolis interactions between $V2=1$ and $v5=1$ levels have beet used in a least squares fit of the intensity data to determine the magnitudes and relative signs of the vibrational transition moments. The density functional method gives excellent agreement with the experimental data as for the signs of the dipole moment derivatives and in most cases a very good agreement as for their absolute values.