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The capture of trapped ultracold neutrons (UCNs) by closed hydrogenousimpurities within a solid coating of the trap is discussed as a possible causeof observed anomalously large losses of UCNs in solid material UCN traps. Thensignificant losses of UCNs arise only if resonances occur in the UCN-impurityscattering amplitude. For a large size impurity, higher partial waves in theUCN-impurity interaction are important, and they are taken into account in thepresent paper. The method of the calculation is applicable to irregular shapeimpurities as well. A small distortion of an impurity shape, if it splits theresonance, can increase the UCN losses by a few times. UCN losses in theberyllium trap are calculated assuming they are due to the UCN capture by icespherical impurities within the coating of the trap walls. Both s- and p-waveresonances contribute significantly to the UCN losses considered. As anexample, observed anomalous large UCN losses are achieved if the average radiusof the impurity is about 600 Angstroms and the impurity density is about3*10^{14}/cm^3. A distortion of the spherical shape of the impurity couldincrease the UCN losses and therefore decrease the impurity density.

Resonance capture by hydrogenous impurities and losses of ultracold neutrons in solid material traps