Can Nuclear Decay constant be Modified ?

The life-time of $^{133}Cs$ in the first excited state has been measured with the M\"ossbauer method by placing the absorber, CsCl, between two parallel flat plates and the gamma-ray source, Ba^*TiO_3, in the free space. The result is 9.37 \pm 0.19 ns, which is 49 percent larger than the standard value 6.27 \pm 0.02 ns.