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Alisdair O. G. Wallis

Alisdair O. G. Wallis
Tesco Plc. United Kingdom · Commercial Science

About

14
Publications
1,259
Reads
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224
Citations
Citations since 2017
2 Research Items
114 Citations
20172018201920202021202220230510152025
20172018201920202021202220230510152025
20172018201920202021202220230510152025
20172018201920202021202220230510152025
Additional affiliations
November 2012 - November 2014
University of London
Position
  • Research Associate
October 2010 - October 2012
University of British Columbia - Vancouver
Position
  • PostDoc Position

Publications

Publications (14)
Article
Full-text available
The complementarity and substitutability between products are essential concepts in retail and marketing. Qualitatively, two products are said to be substitutable if a customer can replace one product by the other, while they are complementary if they tend to be bought together. In this article, we take a network perspective to help automatically i...
Preprint
Full-text available
The complementarity and substitutability between products are essential concepts in retail and marketing. Qualitatively, two products are said to be substitutable if a customer can replace one product by the other, while they are complementary if they tend to be bought together. In this article, we take a network perspective to help automatically i...
Article
Full-text available
Hollow states, containing inner-shell holes, are created by exposure to a Free-Electron Laser (FEL). We compute ion yields and electron spectra, which are experimental observables.
Article
We explore the formation of Ar hollow states with two or three inner-shell holes by free-electron-laser radiation. We find that even-charged Ar ion states can be more populated than odd-charged Ar ion states. This depends on the pulse intensity and the number of energetically accessible inner-shell holes. Fully accounting for fine structure, we dem...
Article
Full-text available
We explore the formation by Free-Electron-Laser radiation of Ar hollow states with two or three inner-shell holes. We find that even charged Ar ion states can be more populated than odd charged Ar ion states. This depends on the pulse intensity and the number of energetically accessible inner- shell holes. Fully accounting for fine structure, we de...
Article
We explore the possibility of retrieving Auger spectra with FEL radiation. Using a laser pulse of 260 eV photon energy, we study the interplay of photo-ionization and Auger processes following the initial formation of a 2p inner-shell hole in Ar. Accounting for the fine structure of the ion states we demonstrate how to retrieve the Auger spectrum o...
Article
Magnetic Feshbach resonances play a central role in experimental research on atomic gases at ultracold temperatures, as they allow one to control the microscopic interactions between ultracold atoms by tuning an applied magnetic field. These resonances arise due to strong hyperfine interactions between the unpaired electron and the nuclear magnetic...
Article
Magnetic Feshbach scattering resonances play a central role in experimental research of atomic gases at ultracold temperatures. A major thrust of current research is to create an ultracold gas of diatomic alkali-metal molecules in the ground rovibrational state of the ground electronic ^1σ state. Can ultracold ^1σ molecules be controlled by means o...
Article
We study the rotational predissociation of atom-molecule complexes with very small binding energy. Such complexes can be produced by Feshbach resonance association of ultracold molecules with ultracold atoms. Numerical calculations of the predissociation lifetimes based on the computation of the energy dependence of the scattering matrix elements b...
Article
We show that conical intersections can be created in laboratory coordinates by dressing a parabolic trap for ultracold atoms or molecules with a combination of optical and static magnetic fields. The resulting ring trap can support single-particle states with half-integer rotational quantization and many-particle states with persistent flow. Two we...
Article
Full-text available
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 and is only weakly...
Article
Full-text available
We calculate the quartet potential energy surface for Li+NH and use it to calculate elastic and spin-relaxation cross sections for collisions in magnetically trappable spin-stretched states. The potential is strongly anisotropic but spin-relaxation collisions are still suppressed by centrifugal barriers when both species are in spin-stretched state...
Article
We carry out calculations on $M$-changing collisions of NH ($^3\Sigma^-$) molecules in magnetically trappable states using a recently calculated potential energy surface. We show that elastic collision rates are much faster than inelastic rates for a wide range of fields at temperatures up to 10 mK and that the ratio increases for lower temperature...
Article
Full-text available
For two states of opposite parity that cross as a function of an external magnetic field, the addition of an electric field will break the symmetry and induce an avoided crossing. A suitable arrangement of fields may be used to create a conical intersection as a function of external spatial coordinates. We consider the effect of the resulting geome...

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