An ultrafast inner-shell ionization process, together with x-ray emiss
ion stimulated by high-intensity short-pulse x rays, is studied. In th
is process it is found that the multi-inner-shell ionization predomina
tes, leading to the formation of hollow atoms. These hollow atoms play
an instrumental role in high brightness x-ray measurements of the ult
rafast dynamics in chemistry, biochemistry, biology, and materials. As
the pumping x-ray power and thus the density of hollow atoms are incr
eased, the emission of x rays is not only of significance for the meas
urement but is good for x-ray lasing. This lasing mechanism has a clea
r advantage over the conventional inner-shell ionization method, yield
ing a gain value of more than 10(4) cm(-1) over a relatively long time
. Classes of experiments of pump x-ray probe and x-ray laser are sugge
sted.