Free-atom Model Research Articles

Experimental and theoretical study of the absorption of ultra-soft x-rays in platinum and tantalum

The photoionization cross-sections of platinum and tantalum, determined experimentally using the Frascati synchrotron radiation in the region of soft X-rays, are compared with the values calculated using a free atom model with central potential.

Determination of the thermal diffusion coefficient for liquid ammonia using pulsed neutron techniques

Measurement of the thermal neutron diffusion coefficient, D 0, and diffusion cooling coefficient, C, for liquid ammonia at its boiling point was made using the 1 MeV Van de Graaff at North Carolina State College. The value for D 0, 21,763 ± 1809 cm 2 sec −1, agrees well with the theoretical prediction of 23,095 cm 2 see −1 using a bound-atom model and with the theoretical prediction of 25,521 cm 2 sec −1 using a free-atom model. The value for C is 6791 ± 2033 cm 4 sec −1, and for λ 0 it is 15,367 ± 297 sec −1 which is near the theoretical value of 15,207 ± 450 sec −1.