Exact results on spin dynamics and multiple quantum dynamics in alternating spin-1/2 chains with XY-Hamiltonian at high temperatures

TL;DR

This paper provides exact solutions for spin dynamics and multiple quantum NMR spectra in alternating spin-1/2 chains with XY-Hamiltonian, revealing how inhomogeneity affects polarization transfer and coherence intensities at high temperatures.

Contribution

It derives the exact spectrum of the XY-Hamiltonian for an alternating chain with odd sites and applies it to analyze MQ NMR dynamics, extending understanding beyond homogeneous chains.

Findings

Exact spectrum of alternating chain with odd sites obtained

MQ coherences of zero and ±2nd order observed in spectra

Calculated intensities of MQ coherences for the inhomogeneous chain

Abstract

We extend the picture of a transfer of nuclear spin-1/2 polarization along a homogeneous one-dimensional chain with the XY-Hamiltonian to the inhomogeneous chain with alternating nearest neighbour couplings and alternating Larmor frequencies. To this end, we calculate exactly the spectrum of the spin-1/2 XY-Hamiltonian of the alternating chain with an odd number of sites. The exact spectrum of the XY-Hamiltonian is also applied to study the multiple quantum (MQ) NMR dynamics of the alternating spin-1/2 chain. MQ NMR spectra are shown to have the MQ coherences of zero and $\pm$ second orders just as in the case of a homogeneous chain. The intensities of the MQ coherences are calculated.