Using data from the semiempirical study of the transition probabilities, radiative lifetimes, and determination of dipole moments of the 3d^1,3Δ_g → 2p^1,3Π_u and 3d^1,3Π_g → 2p^1,3Π_u electronic transitions of the hydrogen molecule as the basis, the probabilities of spontaneous emission for separate rovibronic lines of the i³Π_g^-, j³Δ_g^- → c³Π_u^± and I¹Π_g^-, J¹Δ_g^- → C¹Π_u^± transitions of H₂ are calculated. All the data necessary for determining the populations of the rovibronic levels of the singlet and triplet 3d-complex of terms from the intensities of spontaneous emission from these levels are presented in a form suitable for application. The results of determining the relative populations of rovibronic levels of the i³Π_g^-, j³Δ_g^- and I¹Π_g^-, J¹Δ_g^- states of the H₂ molecule in low-pressure plasma found from the distribution of the relative intensities of lines of the rotational branches of the diagonal bands of the i³Π_g^-, j³Δ_g^- → c³Π_u^± and I¹Π_g^-, J¹Δ_g^- → C¹Π_u^± transitions are discussed. It is shown that the transition probabilities calculated from these data make it possible to obtain consistent information about the distribution of populations over vibration-rotation levels of the Π_g^- and Δ_g^- electronic states of the singlet and triplet 3d-complex of terms of H₂.