The angular correlation functions (ACFs) of a pair of Lyman-α photons emitted from H fragments in the photodissociation of a hydrogen molecule are measured at a 33.66-eV incident photon energy and at hydrogen gas pressures of approximately 0.1 and 1 Pa. The ACFs are measured for both opposite and nonopposite arrangements of the two photon detectors. It turns out that the experimental ACFs involve neither the contribution of the reactions $\mathrm{H}\left(n=2\right)+{\mathrm{H}}_2$ nor the contribution of the cascade from $\mathrm{H}(n$ ⩾ 3) to H($2p)$ fragments. Thus the experimental ACFs are those for primary H($2p)$ pairs following the photodissociation of ${\mathrm{H}}_2$. The experimental ACFs are compared with (i) the theoretical ACF for entangled pairs of H($2p)$ atoms, where the magnetic quantum number of each hydrogen atom is indefinite, and (ii) the theoretical ACF for H($2p)$ pairs with definite magnetic quantum number of each hydrogen atom relative to the internuclear axis [the former entangled state of H($2p)$ pairs is a sum of the latter pair states with definite magnetic quantum number]. In the theoretical ACF in (ii), the disentanglement in H($2p)$ pairs during the dissociation is considered. The experimental ACFs show a similar tendency in angular dependence to the theoretical ACF for entangled H($2p)$ pairs. However, there still remains a considerable difference in the variation magnitude between those experimental and theoretical ACFs. The experimental ACFs show the reverse tendency in angular dependence to the theoretical ACF for H($2p)$ pairs with definite magnetic quantum number of each hydrogen atom relative to the internuclear axis. We thus conclude that the pair of H($2p)$ atoms in the photodissociation of ${\mathrm{H}}_2$ is unlikely to be in the definite states of magnetic quantum number of each hydrogen atom relative to the internuclear axis, i.e., unlikely to be in the components of the entangled state of H($2p)$ pairs.

• Received 3 June 2014
• Revised 16 September 2014

DOI:https://doi.org/10.1103/PhysRevA.90.043405