|Budget Amount *help
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1991 : ¥200,000 (Direct Cost : ¥200,000)
Fiscal Year 1990 : ¥300,000 (Direct Cost : ¥300,000)
Fiscal Year 1989 : ¥1,300,000 (Direct Cost : ¥1,300,000)
Rare-earth N_<4, 5> emission spectra of PrB_6, NdB_6, SmB_6, EuB_6, and GdB_6 have been measured to investigate the 4f states. Photoelectron spectra of some rare-earth compounds have been also measured to determined the binding energies of the 4d and 4f levels and to see the non-radiative decay of the 4d hole states. The N_<4, 5> emission spectra show some, emission peaks above and below the one-electron 4d threshold. The energy positions of these emission spectra are compared with those in the absorption spectra and the existing results of resonant photoemission. Comparison shows that the emission spectra are composed of two types of 4f -> 4d emission processes, i. e., normal emission 4d^94f^n -> 4d^<10>4f^<n-1> + hnu and reemission 4d^94f^n -> 4d^<10>4f^<n-1> + hnu, where n is the number of 4f electrons in th ground state. This result indicates that radiative decay from the 4d^94f^<n+1> excited states above the 4d threshold is expected, even though the interaction between the 4d^94f^
<n+1> states and the continuum is strong and the autoionization channels are present. The spectral profile of reemission is similar to that of the absorption spectra for lighter elements, but it becomes different from the absorption spectra increasing with the atomic number. The energy position of the highest energy peak in reemission is observed a few electron volts below the corresponding absorption peak. However, the energy positions of peaks in reemission coincide with those of the peaks in the constant initial state spectra withthe initial states of the 4f or 5p levels of rare earths though the spectral profile is different from each other.
The intensity ratio of tlie 4f -> 4d to 5p -> 4d is obtained from the emission spectra. This result shows that the 4f -> 4d emission intensity is always less than the 5p -> 4d emission and it decreases with increasing atomic number. On the other hand, simple calculation of intensity ratios of the 4f -> 4d to 5p -> 4d transitions is larger than 1. Fortlier theoretical and experimental investigations of the x-ray emission processes are desired considering interactions among 4d, 4f, and the continuum. Less