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The electronic spectroscopy of $I2$ and IBr, isolated in solid rare gas matrices has been studied using time and wavelength resolved fluorescence techniques. Argon isolated $I2$, excited at a wavelength of 193 nm, showed a broad feature at about 380 nm, that has a very short life-time (= 20 ns). This transition has been tentatively assigned as the $D(3\Pi 2g)-A(3\Pi 2u)$ system. Ar, Kr and Xe isolated IBr, excited at a wavelength of 532 nm, exhibited both $A(3\Pi 1)-X(1\Sigma )$ and $A\prime (3\Pi 2)-X(1\Sigma )$ systems. The life-times of these transitions decrease with increasing atomic number of the host. Spectral and temporal analyses will be discussed.