molscat: A program for non-reactive quantum scattering calculations on atomic and molecular collisions

Abstract

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Characterizing quasibound states and scattering resonances

“…We choose to use equally spaced points separated by a small amount δE, based on a physical estimate of the resonance width. The initial estimate of the resonance position could come from various sources, including approximate calculations or experimental measurements; we usually use the program bound [10,11], which solves the coupled-channel problem subject to bound-state boundary conditions.…”

“…The state with H 2 vibrational quantum number v = 1, rotation j = 0 and total angular momentum J = 0 lies about 4100 cm −1 above the ground state and can predissociate to form H 2 , v = 0, j ≤ 8. We use the interaction potential of Le Roy and Carley [12], and perform close-coupled scattering calculations using the molscat package [11,13] to evaluate the S matrix and its eigenphase sum as a function of energy. We use a space-fixed basis set that includes all functions with j ≤ 10 for v = 0 and with j ≤ 8 for v = 1 and solve the coupled equations using the symplectic log-derivative propagator of Manolopoulos and Gray [14] with the six-step fifth-order symplectic integrator of McLachlan and Atela [15].…”

“…We use the interaction potential of Strauss et al [18], without retardation corrections. We perform coupledchannel calculations using the molscat [11,13] and bound [10,11] packages. The methods used are as described in Ref.…”

Time delays in ultracold atomic and molecular collisions

“…We illustrate the behavior with calculations on resonances in collisions of Rb and Cs atoms. We carry out coupled-channels calculations to evaluate energydependent phase shifts in magnetic fields using the molscat [29,30] package. The methods used are similar to those described in Ref.…”

“…For each resonance we find B pole res (0), a bg , and ∆ from coupled-channels calculations by converging on and characterizing the pole in scattering length using the methods of Frye and Hutson [40]. To obtain µ rel , we carry out coupled-channels calculations of the energy of the bound state in a near-linear region below threshold, using the bound package [30,41]. Table I lists these parameters, together with other relevant quantities including s res and E X , for each of the resonances.…”