We report results of quantitative ultraviolet (UV) and infrared (IR) absorption spectroscopy experiments on Al-atom-doped cryogenic parahydrogen (pH(2)) solids produced by codeposition of Al vapor and pH(2) gas. For Al-atom concentrations [Al] less than or similar to 200 parts-per-million (ppm), the Al/pH(2) solids are optically transparent and primarily contain isolated Al atoms, with a small admixture of AlH, Al2H2, and Al2H4 molecules formed by UV irradiation and Al-atom recombination/reaction. We assign the Al/pH(2) UV absorption spectrum by invoking a large (approximate to 0.6 eV) gas-to-matrix blue shift to accompany the increase in principal quantum number in the 4s S-2 <- 3p P-2(1/2) transition, as previously discussed for boron-atom-doped pH(2) solids. We assign a series of sharp features observed in the 4140-4155 cm(-1) IR region to Al-atom-induced Q(1)(0) and Q(1)(1) absorptions of the pH(2) solid. We use the solid pH(2) Q(1)(0) + S-0(0) absorption to determine the sample thickness and to establish a constant pH(2) deposition efficiency independent of the flow rate. Using all of these absorption features in concert, we show that the Al-atom flux delivered by the effusive source is well described by the Knudsen-Langmuir equation, calculate an absolute Al-atom deposition yield per mass of aluminum evaporated, and demonstrate both constant Al-atom deposition and isolation efficiencies for [Al] less than or similar to 200 ppm. We discuss this unexpected constant Al-atom isolation efficiency in detail and speculate that it indicates nonuniform Al-atom recombination/reaction on the surface of the accreting sample, perhaps dominated by processes occurring near pH(2) crystallite grain boundaries. We demonstrate "control" over the deposition process, which we define as the ability to set, achieve, and verify "targets" for the final Al-atom concentrations and pH(2) solid thicknesses. This ability is key to sorting out the very different phenomena observed in samples targeting [Al] greater than or similar to 300 ppm, which are described in the immediately following companion manuscript.