Intense exact resonance enhancement of single-high-harmonic from an antimony ion by using Ti:Sapphire laser at 37 nm.

We demonstrated the intensity enhancement of a single high-order harmonic at a wavelength of 37.67 nm using the lowly ionized antimony laser-ablation plume. The conversion efficiency of this harmonic was 2.5x10(-5) and the output energy was 0.3 muJ. Such an enhancement of single-harmonic was caused by the multiphoton resonance with the strong radiative transition of the Sb II ions. The cutoff energy of the harmonics generated in Sb plasma was 86 eV (55(th) harmonic).