Knowledge Bank

Two-laser, pump-probe spectroscopy experiments reveal different dissociation pathways for $He\cdots ICl(B,\nu \prime )$ intermolecular levels. Weakly bound $He\cdots I35Cl(B,\nu \prime =3)$ complexes that are prepared with different quanta of intermolecular vibrational excitation are observed to undergo vibrational predissociation to yield predominantly $I35Cl(B,\nu \prime =2)$ products. The $I35Cl(B,\nu \prime =2)$ rotational product state distributions formed following the excitation of different intermolecular vibrational levels and rotational states are all bimodal. Less rotational excitation is found in the products when preparing $He\cdots ICl(B,\nu \prime )$ bending levels that preferentially sample the linear $He-I-Cl$ and anti-linear I-Cl-He orientations than when preparing the lowest intermolecular vibrational energy level, which has a preferred T-shaped geometry. Additionally, linear $He\cdots I35Cl(B,\nu \prime =2)$ complexes undergo a direct dissociation mechanism when prepared above the $He+I35Cl(B,\nu \prime =2)$ dissociation limit. The $I35Cl(B,\nu \prime =2)$ products are formed with significantly less rotational excitation via this mechanism. Dynamical effects believed to be associated with tunneling through the centrifugal barrier are observed and result in highly non-statistical rotational distributions.