STRUCTURES IN THE SPECTRUM OF MULTIPHOTON DETACHMENT RATES OF NEGATIVE-IONS

With the help of a model calculation, the following features in the mu ltiphoton detachment rate spectrum of negative ions are shown: (1) the global behavior of the rate, as a function of the photon frequency, d oes follow the so-called 'step-like' pattern; (2) a Wigner-type cusp o ccurs at every threshold open for the lower photon number channel; (3) a clear dip appears at a certain frequency point slightly lower than each threshold frequency. All these features are interpreted as the ge neral characteristics of multiphoton detachments on the R-matrix-Floqu et analysis. Comparisons are made with the previous results. To the be st of our knowledge, the third feature may be for the first time expla ined in this paper, though it is not first found by us.