No abstract

New experimental data on the secondary electron yield from a thin layer of 57 Fe irradiated by emission of the hot dense plasma source created by femtosecond laser pulses with intensity of 10 17 W cm −2 is presented. Plasma source hard x-ray and electron fluxes are measured for the source characterization. Thorough statistical analysis of the delayed secondary electron spectrum from the 57 Fe layer in the 20-100 ns temporal window allows exclusion of the 'null' hypothesis of the random character of the differences of this spectrum with that obtained using a 56 Fe target. Thus, statistically valid maxima at ∼5.8 and 7.4 keV can be attributed to the decay of the isomeric nuclear state of 57 Fe (3/2 − , 14.41 keV, 98 ns) by the internal conversion process through the atomic K-shell (maximum at 7.4 keV), followed by the Auger process (maximum at 5.8 keV).

No abstract

Enhancement of K α emission from a copper foil covered with micron-sized nanorods with a high aspect ratio is experimentally obtained for perpendicularly incident femtosecond laser pulses. Hot-electron temperature was determined simultaneously with characteristic x-ray measurements. A model of the nanorodsʼ transformation by an amplified spontaneous emission prepulse is suggested. Modeling of the K α yield and hot-electron temperature demonstrates good agreement with the measured values under the assumption that the nanorods are transformed into hemispherical clusters by the prepulse. It is revealed that an increase in K α yield is caused by an increased number of hot electrons at the clustered surface. To increase the conversion efficiencies of the laser pulse energy into hot electrons and x-rays, the foil covered with tightly arranged spherical clusters of optimal size should be used.

No abstract