Refine A1 Ka = 1 origin and upper-state B′ values for the acceptor symmetric O–D stretch

Determine with higher precision the vibrational origin of the A1 Ka = 1 upper state and the upper-state rotational parameter B′ (average of B and C) for all 1s tunneling components, as well as the B′ value for the A2 tunneling component, in the acceptor symmetric O–D stretch fundamental of (D2O)2, which are not well determined due to broadening and limited resolution.

Background

The Ka = 1 ← 0 c-type sub-bands of the acceptor symmetric O–D stretch exhibit significant predissociation broadening, particularly for the A1 component, which hinders precise determination of rotational parameters and vibrational origins.

Accurate upper-state rotational constants and origins are necessary for quantifying tunneling splittings and for comparing with theoretical predictions of vibrational dependence of rotation–tunneling dynamics.