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Resonances in hydrogen atoms in collinear linearly polarized microwave field + static field.
Excited H atoms ionized by contemporaneous pulses of collinear static
Fs and linearly polarized microwave F ω cos(ω t + &phis;) electric fields exhibit strong-field resonances as Fs is slowly swept keeping Fω fixed. These resonances have the following properties: (i) they appear at nearly equally spaced static fields jFs, where j = 1, 2…; (ii) at certain values of the ratio Fω/ Fs they disappear; (iii) as F ω increases their position in Fs decreases nearly linearly; (iv) their widths decrease as disappearance is approached from above and below. For new experiments I modify the microwave cavity to allow observation of resonances that were inaccessible in previous experiments. I make precise measurements of property (ii) and compare experimental data with several theories. Classical Monte Carlo calculations and an analytical classical theory, both carried out by D. Richards, show good agreement with our data. Theoretical models developed for the earlier version of this experiment give good agreement with our data for certain disappearances, but for others there are systematic discrepancies. We also make experimental observations that support recent theoretical work by V. N. Ostrovsky and E. Horsdal-Pedersen that predicts that weak transverse fields, added to Fs and Fω, induce couplings that produce new resonances.