Measuring surface phonons using molecular spin-echo

Abstract

A new method to measure surface phonons with a molecular beam is presented. The method extends the principles of 3He spin-echo spectroscopy, to the more complex case of a molecular...

Temperature dependent stereodynamics in surface scattering measured through subtle changes in the molecular wave function

“…To be able to analyse the data from the experiments, it is necessary to model how each of the m I , m J states of the H 2 molecule interacts with the applied magnetic elds along the beam line of the apparatus. In our previous work, 13,19,20,22 we have used semi-classical trajectory calculations 29 to determine the probability that the different states are transmitted through the rst and second magnetic hexapoles separately, but here we have improved the model to account for the trajectory of the molecules through both arms of the machine, i.e., the probability of a molecule being transmitted through the second hexapole depends on the state it was in when transmitted through the rst due to small but non-negligible changes in the angular and spatial distribution of the beam at the entrance to the second hexapole. As will be shown in a future publication, this modication improves the ts that are obtained to the data but does not have any effect on the conclusions on the stereodynamic properties that are presented here.…”

“…The MMI apparatus has been described previously [18][19][20][21][22][23] and only the details relevant for the current work are presented here.…”

Characterisation of magnetic atomic and molecular beamlines for the extraction of empirical scattering-matrices

“…1. The experimental setup has been described previously, [28][29][30][31][32][33][34] and so only the main details will be presented here with a particular focus on how the different components are simulated which allows signals to be calculated and the S-matrix to be extracted from the data. Here, elastic scattering of H 2 in the I = 1, J = 1 state is considered, which in the presence of a magnetic field can be split into three nuclear spin projection states (m I ) which each split into three rotational orientation projection states (m J ), giving a total of nine m I , m J states, the energies of which can be calculated using the Hamiltonian defined by Ramsey.…”

“…In previous studies 28,30,32,34 the probabilities that the different m I , m J states are transmitted through the second hexapole were approximated as being independent of the probability that they are transmitted through the first, which gave 18 hexapole probabilities, one each for the transmission of the nine initial m I , m J states through the first hexapole, and another nine for the transmission of each of these states through the second hexapole. However, the probability that an m I , m J state will be transmitted through the second hexapole will depend both on its magnetic moment and its trajectory through the machine, which is influenced by the first hexapole.…”