High level ab initio calculations are performed on the ground electronic state of diatomic molecules MgAlk (Alk = Li, Na, K, Rb, Cs). Potential energy curves and dipole moment functions are determined making use of the single-reference unrestricted and restricted coupled-cluster methods with large basis sets. Basic spectroscopic properties of the ground electronic states are derived from ro-vibrational bound state calculations.

Ultracold collisions of the polyatomic species CaOH are considered, in internal states where the collisions should be dominated by long-range dipole-dipole interactions. The computed rate constants suggest that evaporative cooling can be quite efficient for these species, provided they start at temperatures achievable by laser cooling. The rate constants are shown to become more favorable for evaporative cooling as the electric field increases. Moreover, long-range dimer states (CaOH) 2 * are predicated to occur, having lifetimes on the order of microseconds. which is exothermic by some 13 000 K. Ca(OH) 2 is a stable compound used in industrial applications like paper production and sewage treatment. It is not known whether the reaction (1) occurs at low temperatures in the gas phase. If it does, this is obviously a detriment to producing and maintaining a stable, ultracold gas of CaOH. We will disregard the possibility that the reaction occurs, both because the potential energy surface is unknown, and because, in the appropriate internal states, the molecules are expected to be shielded by the repulsive parts of the dipole-dipole interaction.This circumstance simplifies the description of scattering, and leads to certain common behaviors. In this article, exploiting the electric dipole moment of CaOH and considering a state that has a small parity doublet, we find that these behaviors still occur. The behaviors that we single out are: (1) a suppression of inelastic scattering at sufficiently high electric field and sufficiently low temperature, for states that can be optically trapped; and (2) a set of electric-field resonances, previously described as 'field linked states', [16,17] that could serve as an additional platform for controlling these species and their interaction.

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A model is presented that mimics the nearest-neighbor-spacing (NNS) distribution of chaotic molecules such as Dy2 and Er2 just below their dissociation threshold. In this model the degree of chaos is controlled by choosing suitable Hamiltonian matrices from random ensembles. It is found that, in versions of the model that are not completely chaotic, the NNS of observable Fano-Feshbach resonances exhibits greater level repulsion, hence more chaos, than the corresponding NNS of a typical energy spectrum of the molecule at a fixed magnetic field.