  High resolution Fulcher band spectroscopy was used in the MAST-U divertors
during Super-X and elongated conventional divertor density ramps with
$\text{D}_{2}$ fuelling from the mid-plane high-field side. In the Super-X case
(density ramp from Greenwald fraction 0.12 to 0.24), the upper divertor showed
ground state rotational temperatures of the $\text{D}_{2}$ molecules increasing
from $\sim$6000 K, starting at the detachment onset, to $\sim$9000 K during
deepening detachment. This was correlated with the movement of the Fulcher
emission region, which is correlated with the ionisation source. The increase
in rotational temperature did not occur near the divertor entrance, where the
plasma was still ionising. Qualitative agreement was obtained between the lower
and upper divertor. Similar rotational temperatures were obtained in the
elongated divertor before the detachment onset, although the increase in
rotational temperature during detachment was less clearly observed as less deep
detachment was obtained. %In the elongated conventional divertor there was some
qualitative agreement of this effect impeded by low signal.
  The measured vibrational distribution of the upper Fulcher state (first four
bands) does not agree with a ground state Boltzmann distribution but shows a
different characteristic with an elevated population especially in the $\nu =
2$ and $\nu = 3$ bands. The populations of the $\nu = 2$ and $\nu = 3$ band
relative to the $\nu = 0$ band are roughly proportional to the
$\textit{rotational}$ temperature.
