The dipole moments of OCS for several isotopic species and vibrational states have been determined from the Stark splitting of the $J=1\mathrm{}\to 2$ rotational transition. The value of the ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{32}$ moment is 0.7085±0.004 debye units. The ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{34}$ and ${\mathrm{O}}^{16}$${\mathrm{C}}^{13}$${\mathrm{S}}^{32}$ moments differ from this by less than 0.2 percent. The ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{32}$ molecule in the excited bending mode ($v_2=1\mathrm{}$) is treated formally as a slightly asymmetric top which produces a doublet. Measurement of Stark effect for these lines gives a dipole moment of 0.700±0.004 debye. Upon introduction of a Stark voltage, two weak lines appear on either side of the doublet $v_2=1\mathrm{}$. They are explained as transitions involving the doublet levels which are forbidden in zero field, but allowed upon the introduction of a perturbing field.

• Received 3 October 1949

DOI:https://doi.org/10.1103/PhysRev.77.500