Abstract
It is widely believed that the hyperfine states must be resolved in one way or the other to measure the degree of nuclear-spin polarization of atoms and ions. We theoretically show that the angle-resolved photoelectron signals produced by resonant multiphoton ionization by short and hence broadband two-color laser pulses, which cover all fine-structure and hyperfine manifold of the ground and resonant excited states, can serve as a new type of nuclear-spin polarimeter. Because of the use of time-delayed short laser pulses the proposed method has very high (subnanosecond) time resolution, and does not suffer from the Doppler broadening. Specific results are presented for the two-photon resonant three-photon ionization of hydrogen atoms using 205- and 410-nm laser pulses with picosecond to femtosecond pulse durations. The proposed scheme is immediately applicable to other unstable elements such as 11Be+, 27Mg+, and 35Ca+, etc.