摘要
Constraining ionization and excitation processes in protoplanetary disks is essential for understanding the chemical structure and evolution of disk material, shaping planet formation pathways. We present JWST/NIRSpec IFU observations of the edge-on disk Oph 163131, which reveal a unusual ro-vibrational H ₂spectrum dominated by the 1–0 O(2) line (2.627μ m), with suppressed higher- Jemission despite excitation tov=2and3 . This vibrationally hot, rotationally cold H ₂emission is spatially extended, broadly following the molecular disk traced by CO( J=2 –1), with emission increasing above and below a thin midplane dark lane and extending radially beyond∼ 200 au, where near-IR scattered-light emission is no longer dominant. We interpret the observed H ₂emission as arising from non-thermal excitation in cold, dense outer-disk gas, where collisions depopulate higher- Jrotational levels within each vibrational manifold prior to emission, producing the characteristic `` v -hot,J -cold" spectrum. We consider both ultraviolet irradiation and cosmic-ray excitation as contributors to the H ₂emission and find that their combined action, together with collisional de-excitation of high- Jlevel populations, broadly reproduces the observed line ratios and morphology. Within this framework, we infer a rather high effective cosmic-ray ionization rate of∼(1 - 10)×10⁻¹⁵s ⁻¹in the presence of a moderate UV field ( χ_(UV)=100-1000 , in Draine units). These results for disks, together with the recent findings by Bialy et al. 2025 for the lower-density starless core B68, highlight the potential of ro-vibrational H ₂emission as a novel probe of cosmic-ray ionization.