We have carried out Ru-101 NQR measurement of URu2Si2 in zero magnetic
field in the temperature (T) range from 0.16 to 130 K. The electric q
uadrupole interaction parameters of Ru-101 were determined to be nu(Q)
= 5.72 MHz and eta = 0 at 1.3 K. Although URu2Si2 is in the antiferro
magnetic (AF) state below 17.5 K, no broadening of NQR line was observ
ed, indicating that transferred hyperfine field from U moments is canc
elled at Ru site. The nuclear spin-lattice relaxation rate (1/T-1) dec
reases drastically below 17.5 K associated with AF ordering. In the su
perconducting state, 1/T-1 has no coherence peak just below T-C = 1.2
K, and decreases in proportion to T-3 With no deviation down to 0.2 K,
which shows the existence of line nodes in the superconducting energy
gap.