Interstellar dust plays a crucial role in understanding the chemical complex ity in the interstellar medium. However, dust formation itself has not been fully understood. Evolved stars are identi ed as a source for interstellar dust grains. Molecules, comprised of refractory elements, form in the inner envelope of evolved stars. These molecules are considered to initiate dust formation. Thus, their detection will provide new insights into the process of dust forma tion. Evolved stars suit infrared observations well. Yet laboratory infrared spectra of these molecules are rather sparse. This work presents laboratory studies of transient molecules associated with the inner envelope of evolved stars. The molecules TiO, Al2O and Si2C are produced in a laserablation source. Infrared radiation of quantum cascade lasers allowed the record of high-resolution spectra. In addition to the transition frequencies, the molecular structures and potentials are determined. The results will enable a dedicated search for these species in dust forming stellar environments. This work concludes by examining infrared spectra of the evolved star VY CMa, which provide physical conditions of its envelope.weiterlesen