Spin-rotation measurements and magnetic shielding in CH₂CF ₂

Rotational transitions 1₀₁→0₀₀, 2 ₁₂→1₁₁, 2₁₁→2₁₂, and 3₂₁→3₂₂ of 1,1 difluoroethylene were studied using a molecular beam maser spectrometer. Emission transitions were observed with 6 kHz linewidth (FWHM) and hyperfine structure due to fluorine and hydrogen interactions was resolved. The diagonal elements of the fluorine spin-rotation tensor are M_aa=-13.4±3.6 kHz, M_bb=-10.94±0. 68 kHz and M_cc=-6.06 ±0.68 kHz. This data is used to determine paramagnetic contributions to the fluorine chemical shift tensor. Analysis of the data yielded line centers for the rotational transitions of 15774348 ±3 kHz for 1₀₁→-0₀₀, 26465055±5 for 2₁₂→1₁₁, and 14419906±3 kHz for 3 ₂₁→3₂₂, and 15250615±3 kHz for 2 ₁₁→2₁₂. Results of semiempirical calculations of diamagnetic contributions to the shielding tenors are presented for CH ₂CF₂ and other molecules. Comparisons of total shielding tensors are made for related molecules.