Absolute and spatially resolved hydrogen densities were measured in a silane radio frequency discharge by two-photon laser induced fluorescence spectroscopy. The excitation wavelength was 205 nm and the observation wavelength was 656 nm (Balmer alpha). Titration in a flow tube reactor was used for calibration of the detection system, enabling for the first time the determination of reliable absolute hydrogen densities in a silane discharge. In addition, spontaneous as well as laser induced powder formation was observed.