The study investigates the laser excitation of the ${}^{229}$Th nuclear isomeric transition in LiSrAlF$_6$ crystals doped with ${}^{229}$Th. Two spectroscopic features near the nuclear transition energy are observed: a broad excitation feature with a decay time of a few seconds and a narrow, laser-linewidth-limited spectral feature at 148.38219(4) nm (2024047.3) GHz, decaying with a lifetime of 568(13) s. The narrow feature is assigned to the excitation of the ${}^{229}$Th nuclear isomeric state, with an energy of 8.355733(2) eV in ${}^{229}$Th:LiSrAlF$_6$. The results are interpreted using *ab initio* crystal structure calculations, suggesting that the short-time fluorescence could be due to coupling of the ${}^{229}$Th nucleus to the electronic and phononic degrees of freedom of the crystal. The findings open up possibilities for novel applications, such as constructing an optical nuclear clock and testing the variation of fundamental constants.The study investigates the laser excitation of the ${}^{229}$Th nuclear isomeric transition in LiSrAlF$_6$ crystals doped with ${}^{229}$Th. Two spectroscopic features near the nuclear transition energy are observed: a broad excitation feature with a decay time of a few seconds and a narrow, laser-linewidth-limited spectral feature at 148.38219(4) nm (2024047.3) GHz, decaying with a lifetime of 568(13) s. The narrow feature is assigned to the excitation of the ${}^{229}$Th nuclear isomeric state, with an energy of 8.355733(2) eV in ${}^{229}$Th:LiSrAlF$_6$. The results are interpreted using *ab initio* crystal structure calculations, suggesting that the short-time fluorescence could be due to coupling of the ${}^{229}$Th nucleus to the electronic and phononic degrees of freedom of the crystal. The findings open up possibilities for novel applications, such as constructing an optical nuclear clock and testing the variation of fundamental constants.