Picosecond kinetic confirmation of overlapping Ca cluster and MNa absorption bands in UV grade CaF2
in: Journal of Applied Physics (2011)
The ArF laser induced absorption feature between 450 and 700 nm observed in the bulk of mono crystalline calcium ﬂuoride (CaF2) upon prolonged 193 nm irradiation is shown to have two origins: The ﬁrst band at 530 nm is revealed by a transient femtosecond (fs) laser transparency spectrum and attributed to Ca clusters (colloid). The second band at 600 nm originates from MNa centers as identiﬁed by their laser induced ﬂuorescence excitation spectrum, emission wavelength, and ﬂuorescence lifetime. The analysis of the absorption feature by fs pump-probe techniques beneﬁts from the different lifetimes of the transient transparency (excited states of the Ca clusters) and the ﬂuorescing MNa centers of about 5 ps and 22 ns, respectively.