The15N/14N isotope shift on the15N chemical shielding in a mixture of15N14N and15N15N was found to be 0.0601plusmn;0.0022 ppm. Using a model developed by Jameson, the nuclear shielding derivative with respect to bond length was calculated from the measured isotope shift, lsqb;part;sgr;(15N)/part;rrsqb;e=minus;910plusmn;42 ppm/Aring;. This value is in excellent agreement with a value obtained from the temperature dependence of the shielding constant in the gas phase (at the zero pressure limit) and with a value determined from recent molecular orbital calculations. From relaxation measurements the scalar spinndash;spin coupling constant,1J(14N,15N), in14N15N was calculated to be 1.8plusmn;0.6 Hz which gives a reduced coupling constant,1K(N,N)=2.0plusmn;0.7 (1020)mminus;2kgthinsp;sminus;2thinsp;Aring;minus;2. The magnitude of the reduced coupling constant is compared to that of other isoelectronic species and molecular orbital calculations.
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