Theoretical study of H2+ spectroscopic properties. II. The 2p πu electronic state

Vibration‐rotation eigenenergies are computed for the (2pπ_u) ²Π_u state of ${\mathrm{H}}_2^{+}$ . Spectroscopic constants Y_ij are found from Dunham power series expansions of the vibrational potential and also from the eigenenergies. The Y_ij are much smaller in magnitude than ${\mathrm{H}}_2^{+}$ ground state values because of the 2p π_u broadened potential and larger equilibrium separation r_e. The eigenenergies are used to determine B_ν, D_ν, and H_ν for all bound vibrational states, i.e., for 0 ≤ ν ≤ 11. Both the ΔG and B_ν curves have negative curvature at all ν. The D_ν and H_ν curves are similar in shape to the respective curves for the ${\mathrm{H}}_2^{+}$ ground state. The D_ν's decrease slowly at low ν but increase rapidly near dissociation. The H_ν curve has a small negative initial slope; the H_ν's decrease very rapidly, becoming negative, at high ν. Origin wavelengths are listed for a few ${\mathrm{H}}_2^{+}$ 2p π_u−1sσ_g bands predicted to be intense on the basis of the classical Franck‐Condon principle; these lie in the Lyman α region.