Absolute cross sections for electron capture into the 3p and 3d states of hydrogen have been measured for 10- to 100-keV proton impact on He, Ne, Ar, H2, N2, and O2. Improved 3s cross sections are presented for these gases from 10 to 120 keV. An apparent maximum in the 3p cross section occurs in this energy range for all gases. The 3d cross sections decrease monotonically with increasing impact energy according to an exp[-(EK)12] relationship, where E is the impact energy and K is a constant, with the exception of helium which shows a maximum in the 3d cross section between 15 and 20 keV. The value of K is identical for all the diatomic gases. Balmer-α cross sections are synthesized from these results. Polarization of the 3d-->2p radiation is reported.