  Low-energy cosmic rays (LECRs) contribute substantially to the energy balance
of the interstellar medium. They play also significant role in the heating and
chemistry of gas, and, consequently, on the star formation process. Because of
the slow propagation coupled with enhanced energy losses of subrelativistic
particles, LECRs are concentrated around their acceleration sites. LECRs
effectively interact with the ambient gas through nuclear reactions. Although
these processes are energetically less effective compared to heating and
ionization, they are extremely important from the point of view of nuclear
de-excitation lines, which carry unique information about LECRs. We present
results on production of de-excitation lines combining the numerical treatment
of nuclear reactions using the code TALYS, with the propagation and energy
losses of LECRs.
