Collisional quenching of molecular ro-vibrational energy by He buffer loading at ultralow energies†

Abstract

In the present review we summarize in some detail the ample theoretical literature which has discussed over the last few years the computational treatment of collisionally inelastic processes at ultralow temperatures. The analysis is centred on the ab initio quantum treatment of collisional quenching of ro-vibrational states of simple diatomics, neutral and ionic, polar and homonuclear, interacting with a helium buffer gas. Several specific examples are analysed and their features are linked with both the details of their interaction potential energy surfaces and the special behavior of ultralow energy quantum dynamics. †This work is affectionately dedicated to the late Roger Miller, a brilliant scientist and a dear friend whose early departure has left a great void in our midst. Contents page 1. Introduction 314 2. The theoretical machinery 317 2.1. Zeeman depolarization 319 2.2. Ultralow energy collisions 319 3. Rotational quenching 321 3.1. Neutral systems with closed-shell molecules 322 3.2. Neutral systems with open-shell molecules 326 3.3. Ionic systems 329 4. Vibrational quenching 334 4.1. Quenching from low ν states 335 4.2. Quenching from high ν states 340 4.3. Ionic systems: virtual state scattering 343 5. Present conclusions 348 Acknowledgments 348 References 348