Abstract: An absorber or desorber contains a layer (10) for a structured packing which has corrugations, wherein a plurality of open channels (12, 14, 16) is formed by the corrugations, wherein the channels include a first corrugation valley (22), a first corrugation peak (32) and a second corrugation peak (42). The first corrugation peak (32) and the second corrugation peak (42) bound the first corrugation valley (22), wherein the first and second corrugation peaks have a first apex (33) and a second apex (43). An indentation (34) extending in the direction of the first apex (33) is formed on the first apex (33) of the first corrugation peak (32). The first corrugation valley (22) has a valley bottom (23), wherein the normal spacing (27) of at least one point of the indentation (34) from the valley bottom (23) of the corrugation valley (22) is smaller than the normal spacing (28) of the first apex (33) from the valley bottom (23) of the corrugation valley (22).