Infrared Spectrum and Molecular Constants of CD4

The infrared spectrum of CD₄ has been examined from 900 cm^—1 to 8500 cm^—1. A total of twenty‐eight bands were observed, including four originally measured by Nielsen and Nielsen under somewhat lower resolving power. Twenty‐three bands were attributed to CD₄, two to CD₃H, two to CH₄, and one was unassigned. With the aid of the band centers of the corresponding fundamentals in CH₄, the following vibrational constants of CD₄ were obtained: the normal frequencies ${\mathrm{\omega ̃}}_1\text{=2143.2}$ , ${\mathrm{\omega ̃}}_2\text{=1109.4}$ , ${\mathrm{\omega ̃}}_3\text{=2336.8}$ , ${\mathrm{\omega ̃}}_4\text{\hspace{0.17em}1026.8\hspace{0.17em}}{\mathrm{cm}}^{\text{−1}}$ ; the harmonic potential energy constants k₁=2.093×10⁵, k₂=2.841×10⁵, k₃=8.463×10⁵, k₄=2.790×10⁵, k₅=1.329×10⁵ dynes/cm. From the rotational analysis of nine bands, the B values of the upper states for these modes of vibration were found as well as the following rotational constants: the vibration‐rotation interaction constants α₁=—0.017, α₂=—0.015, α₃=0.014, α₄=0.017 cm^—1; B₀=2.591 cm^—1; B_e=2.614 cm^—1; I_e=10.70×10^—40 g‐cm²; r_C—D=1.095×10^—8 cm; r_D—D=1.788×10^—8 cm; and the moduli of the internal angular momentum ζ₃=0.14₅, ζ₄=0.35₅.