  We perform ab-initio calculations needed to predict the cross-section of an
experimentally accessible (1+1') resonance-enhanced multiphoton dissociation
(REMPD) pathway in AlH+. Experimenting on AlH+ ions held in a radiofrequency
Paul trap, we confirm dissociation via this channel with analysis performed
using time-of-flight mass spectrometry. We demonstrate the use of REMPD for
rotational state analysis, and we measure the rotational distribution of
trapped AlH+ to be consistent with the expected thermal distribution. AlH+ is a
particularly interesting species for ion trap work because of its electronic
level structure, which makes it amenable to proposals for rotational optical
pumping, direct Doppler cooling, and single-molecule fluorescence detection.
Potential applications of trapped AlH+ include searches for time-varying
constants, quantum information processing, and ultracold chemistry studies.
