CROFT, JAMES,FRANCIS,EDWARD (2012) Cold molecular collisions: eﬃcient methods for quantum calculations. Doctoral thesis, Durham University.
|PDF (Phd Thesis) - Accepted Version|
Multichannel Quantum Defect Theory (MQDT) is shown to be capable of producing quantitatively accurate results for low-energy atom-molecule scattering calculations. With a suitable choice of reference potential and short-range matching distance, it is possible to deﬁne a matrix that encapsulates the short-range collision dynamics. Multichannel quantum defect theory can provide an eﬃcient alternative to full coupled-channel calculations for low-energy molecular collisions. However, the eﬃciency relies on interpolation of the Y matrix that encapsulates the short-range dynamics. It is shown how the phases of the MQDT reference functions may be chosen so as to remove such poles from the vicinity of a reference energy and dramatically increase the range of interpolation. For the test cases of Mg+NH and Li+NH, the resulting optimized Y matrix may be interpolated smoothly over an energy range of several Kelvin and a magnetic ﬁeld range of over 1000G. Calculations at additional energies and ﬁelds can then be performed at a computational cost that is proportional to the number of channels N and not to N cubed. MQDT thus provides a promising method for carrying out low-energy molecular scattering calculations on systems where full exploration of the energy and the ﬁeld dependence is currently impractical.
|Item Type:||Thesis (Doctoral)|
|Award:||Doctor of Philosophy|
|Keywords:||Phd Thesis; Cold molecular collisions; quantum calculations; MQDT|
|Faculty and Department:||Faculty of Science > Chemistry, Department of|
|Copyright:||Copyright of this thesis is held by the author|
|Deposited On:||30 Nov 2012 10:58|