Abstract
The generation of coherent radiation at four new frequencies (59.1, 62.6, 71.0, and 76.0 nm) in the XUV by fifth-order frequency mixing of harmonics from a Nd : YAG laser is reported. The relative strength of the fifth-order mixing processes in He and Ne is discussed. Comparison of fifth and third harmonic generation in He shows higher conversion to the fifth harmonic for sufficiently tight focusing.