FTP, name this quantity denoted J and measured in Hertz, the spacing between associated peaks on an NMR spectrum.   
The relationship of this value to the dihedral angle between protons is given by the Karplus equation in NMR; that result was obtained when this value was seen to have non-zero magnitude between vicinal hydrogen nuclei. FTP, name this quantity denoted J and measured in Hertz, the spacing between associated peaks on an NMR spectrum.   
The relationship of this value to the dihedral angle between protons is given by the Karplus equation in NMR; that result was obtained when this value was seen to have non-zero magnitude between vicinal hydrogen nuclei.
coupling constant (or accept "J" or "3J" before J is mentioned)