Microwave spectrum, structure, dipole moment and excited vibrational states of 1,3,3,3-tetrafluoropropyne, CF3C CF

Abstract

The microwave spectrum of four isotopic species of CF₃CCF have been investigated in the frequency range 9–41 GHz. The zero-point average structure of the carbon skeleton has been unambiguously determined, and with one assumption the average parameters of the fluorine atoms calculated as: r(CC)= 1.202(2)Å, r(C–C)= 1.457(3)Å, r(C–F)= 1.339(2)Å, ∠FCF = 108.02(20)° and r(C–F)_term= 1.274(4)Å.

From Stark-effect measurements the ground-state dipole moment has been determined to be 1.699(4) D (1 D = 3.335 64 × 10^–30 C m). Two vibrational satellite series arising from the degenerate bending motions ν₁₀ and ν₉ have been assigned. The lowest, ν₁₀, is determined to have a wavenumber of 111(8) cm^–1 from the I-type doubling constant q₁₀= 1.215(2) MHz, in good agreement with relative intensity measurements. The I-type resonance in the v₁₀= 1 state has been analysed. For v₉= 1 I-type doubling has been measured giving q₉= 0.550(8) MHz.