Triggering of nuclear isomers by X-ray laser

We studied the decay of nuclear isomeric states in the field of the X-ray laser. The laser pulses are described by the Gaussian wave packet of linearly polarized electromagnetic waves. At first stage the laser short pulse generates nuclear transition in the intermediate excited state, which afterwards decays into the final state with emission of γ quantum. Simple formulas are derived for the induced transition probability, which well correlate with known results, obtained previously for the incoherent X-ray radiation.