Toward understanding the role of Stark effects when probing the nuclear hyperfine states of atomic hydrogen

A variation on velocity-aligned Doppler spectroscopy is used to probe the nuclear hyperfine states of atomic hydrogen resulting from the 193 nm photodissociation of HBr. By utilizing 1 + 1 resonance-enhanced ionization through the Lyman-α transition along with a novel experimental approach, one can observe the onset of Stark effects that come about because of the modest electric field present in the ionization region of the mass spectrometer. A straightforward theoretical treatment is used to address the observed behavior.