Femtosecond relaxation kinetics of highly excited mathrm{M}_{mathrm{Na}}^{**} states in CaF2 at 3.2 eV and 4.7 eV

Femtosecond (fs) laser pulses at variable delay times allowed us to track the fast non-radiative transitions between the manifold of highly excited $mathrm{M}_{mathrm{Na}}^{**}$ states to the lower lying fluorescent $mathrm{M}_{mathrm{Na}}^{*}$ state in CaF₂. Two distinct $mathrm{M}_{mathrm{Na}}^{**}$ states of the manifold at 3.16?eV ( $mathrm{M}_{mathrm{Na}2}^{**}$ ) and 4.73?eV ( $mathrm{M}_{mathrm{Na}3}^{**}$ ) were populated using the second (SH) and third harmonics (TH) of fs laser light at 785?nm. The population kinetics of the fluorescent $mathrm{M}_{mathrm{Na}}^{*}$ state in the 2?eV excitation energy range was revealed by depleting its fluorescence centered at 740?nm using fundamental near infrared (NIR) fs laser pulses. The related time constants for $mathrm{M}_{mathrm{Na}2,3}^{**}{sim}{>} mathrm{M}_{mathrm{Na}}^{*}$ relaxation amounted to 1.0±0.14?ps and 3.0±0.3?ps upon SH and TH excitation, respectively.