Because a 129Xe nucleus have a spin of 1 / 2 , and therefore a zero electric quadrupole moment , the 129Xe nucleus do not experience any quadrupolar interactions during collisions with other atoms , and thus its hyperpolarization can be maintained for long periods of time even after the laser beam have been turned off and the alkali vapor removed by condensation on a room @-@ temperature surface . Spin polarization of 129Xe can persist from several seconds for xenon atoms dissolved in blood to several hours in the gas phase and several days in deeply frozen solid xenon . In contrast , 131Xe have a nuclear spin value of 3 ⁄ 2 and a nonzero quadrupole moment , and have t1 relaxation times in the millisecond and second ranges .