Microwave spectra of four new perfluoromethyl polyyne chains: trifluoropentadiyne, CF/sub 3/-C identical to C-C identical to C-H, trifluoroheptatriyne, CF/sub 3/-C identical to C-C identical to C-C identical to C-H, tetrafluoropentadiyne, CF/sub 3/-C identical to C-C identical to C-F, and trifluoromethylcyanoacetylene, CF/sub 3/-C identical to C-C identical to N