Measurement of Photoionization Cross Section from the 3s3p1p1excited State of Magnesium

The photoionization cross section from the 3s3p P-1(1) excited state has been measured in the energy region from the first ionization threshold up to 1.4 eV excess energy using a two- step photoionization and saturated ionization technique in conjunction with an atomic beam source and a time- of- flight mass spectrometer that enables the separation of the three stable isotopes of magnesium on the time axis. The absolute value of the photoionization cross sections from the 3s3p P-1(1) excited state near the 3s ionization threshold has been measured as 90 +/- 16 Mb (at 354.5 nm ionizing wavelength) for the dominating isotope (Mg-24) whereas the value at the peak of the 3p(2) S-1(0) auto-ionizing resonance has been determined as 785 +/- 141 Mb. The present experimentally measured photoionization cross sections are compared with the existing experimental and theoretical work, showing excellent agreement.