  We describe an apparatus to study the fragmentation of ion-molecule clusters
triggered by laser excitation and transfer of an electron from the iodide to
the neutral molecule. The apparatus comprises a source to generate ion-molecule
clusters, a time-of-flight (TOF) spectrometer and a mass filter to select the
desired anions, and a linear-plus-quadratic reflectron mass spectrometer to
discriminate the fragment anions after the femtosecond laser excites the
clusters. The fragment neutrals and anions are then captured by two channeltron
detectors. The apparatus performance is tested by measuring the photofragments:
I$^-$, CF$_3$I$^-$ and neutrals from photoexcitation of the ion-molecule
cluster CF$_3$I$\cdot$I$^-$ using femtosecond UV laser pulses with a wavelength
of 266 nm. The experimental results are compared with our ground state and
excited state electronic structure calculations and the existed results and
calculations, with particular attention to the dynamics of the photoexcitation
and photodissociation.
