Table 1. Absolute Values of the Dipole Derivatives Computed at Zero Field for the Totally Symmetric Stretching Modes (a) and Bending Modes (b) of the Molecules Investigated in This Work^a.

molecule	ν̅ (cm–1)	|(∂μx/∂qk)0| (debye Å–1 amu–1/2)
H2S	2733(a)	0.07
NH3	3497(a)	0.31
H2O	3853(a)	0.33
HF	4169(a)	1.61
H2S	1221(b)	0.14
H2O	1659(b)	1.32
NH3	1067(b)	1.79

^aResults are from the CCSD/aug-cc-pVTZ frequency calculations. The conversion factor from debye Å^–1 amu^–1/2 to atomic units (as in Table 2) is 4.876 × 10^–3. The x-axis is oriented along the molecular dipole. Since all the reported modes belong to the totally-symmetric irreducible representation, the dipole derivatives are oriented along the symmetry axis of the molecules, which corresponds to the x-axis, i.e., (∂μ_y/∂q_k)₀ = (∂μ_z/∂q_k)₀ = 0.