Search for triple and quadruple beta decay of Nd-150

Triple beta decay of Nd-150 to the ground and excited states of Eu-150 and quadruple beta decay of Nd-150 to the excited states of Gd-150 have been studied using a 400 cm(3) low-background high-purity germanium detector and an external source consisting of 3046 g of natural Nd2O3 powder. A half-life limit for the quadruple beta decay to the 0(1)(+) state of Gd-150 was found to be T-1/2 (0 nu + 4 nu) > 8.7 x 10(20) yr (90% C.L.). For other (0 nu + 4 nu) transitions to the 2(1)(+), 3(1)(-), 4(1)(+), 2(2)(+), and 2(3)(+) excited states limits have been obtained for the first time at the level of (6.1-9.5) x 10(20) yr (90% C.L.). We report here also the results for the first search for triple beta decay to the ground and excited final states of( 150)Eu. We find no evidence of this decay and set lower limits on the half-life in the range T-1/2 (0 nu + 3 nu) > (0.04 - 4.8) x 10(20) yr (90% C.L.).