Experimental study of stark effects in argon high Rydberg states

We examined the Stark effects of argon high Rydberg states in well-defined electric fields by laser-induced fluorescence-dip spectroscopy. The excitations to Rydberg states were carried out from the 4p[3/2](2) state, which was populated by the excitation from the metastable 4s[3/2]degrees(2) state. We observed forbidden transitions from the 4p[3/2](2) to np[312]1,2 states in 2 electric fields. The forbidden transitions were caused by Stark mixing between the np[3/2]1,2 states and the neighboring (n - 1)d[ 1 /2]degrees(1) and (n - 1)d[3/2]degrees(2) states. The energy levels of the np states shifted with an increase in the electric field 1 2 strength. The magnitude of the Stark shift was proportional to the square of the electric field strength. In stronger electric fields, the dip spectra showed oscillating structures, indicating Stark splitting of energy levels. The intervals among the dip peaks induced by Stark splitting were proportional to the electric field strength.