Enhancement of photoionization by applying polarization-based common level excitation scheme for the selective photoionization of odd isotopes of samarium

Due to the importance of Sm-149 isotope in the nuclear industry, isotope-selective photoionization of the odd isotopes of samarium has been studied using multi-color photoionization technique. The present work has been carried out in an atomic beam coupled to a linear time-of-flight mass spectrometer using multimode dye lasers. A new photoionization scheme: 292.58 cm(-1)-> 17,769.71 cm(-1)-> 34,929.9 cm(-1)-> continuum with the J-value sequence 1-1-0-continuum has been identified for the enrichment of only odd isotopes using linearly polarized lasers in the same direction. This photoionization scheme in combination with the first-step transition: 0 cm(-1)-> 17,769.71 cm(-1) (I=0 -> J=1) has been utilized to realize a common level excitation scheme which has significantly increased the photoionization yield of the odd isotopes and suppressed the ionization of the even isotopes of samarium using suitable choice of laser polarization. To enhance the photoionization yield further, a search for the third-step transition terminating into an autoionization level has been carried out. A strong autoionization resonance at the third-step laser wavelength 644.14 nm, corresponding to the transition 34,929.9 cm(-1)-> 50,450.3 cm(-1) has been identified. The J-value of the newly discovered autoionization level at 50,450.3 (+/- 0.5) cm(-1) has been uniquely assigned as J=1. Finally, the photoexcitation/photoionization cross sections of all the transitions involved in the common level excitation scheme including that of the third-step transition terminating into the autoionization level have been measured by saturation method. (C) 2019 Elsevier Ltd. All rights reserved.