Quadrupole Effects on Nuclear Magnetic Resonance Gyroscopes

TL;DR

This paper theoretically investigates how electric quadrupole interactions affect the accuracy of nuclear magnetic resonance gyroscopes, revealing conditions under which quadrupole shifts can be minimized or restored to single-frequency precession.

Contribution

It provides a theoretical analysis of quadrupole effects on NMR gyroscopes, showing how feedback drive strength influences quadrupole-induced frequency shifts and spin precession behavior.

Findings

Quadrupole shift decreases with increasing feedback drive when $C_q$ is small.

Multiple precession frequencies can occur for large $C_q$, depending on initial conditions.

Large driving amplitudes can restore single-frequency precession in high $C_q$ regimes.

Abstract

Nuclear magnetic resonance gyroscopes that detect rotation as a shift in the precession frequency of nuclear spins, have attracted a lot of attentions. Under a feedback-generated drive, the precession frequency is supposed to be dependent only on the angular momentum and an applied magnetic field. However, nuclei with spins larger than 1/2, experience electric quadrupole interaction with electric field gradients at the cell walls. This quadrupole interaction shifts the precession frequencies of the nuclear spins, which brings inaccuracy to the rotation measurement as the quadrupole interaction constant $C_q$ is difficult to precisely measure. In this work, the effects of quadrupole interaction on nuclear magnetic resonance gyroscopes is theoretically studied. We find that, when the constant $C_q$ is small compared to the characteristic decay rate of the system, as the strength of the feedback-driving field increases, the quadrupole shift monotonically decreases, regardless of the sign of $C_q$. In large $C_q$ regime, more than one precession frequency exists, and the nuclear spins may precess with a single frequency or multi-frequencies depending on initial conditions. In this regime, with large driving amplitudes, the nuclear spin can restore the single-frequency-precession. These results are obtained by solving an effective master equation of the nuclear spins in a rotating frame, from which both the steady-state solutions and dynamics of the system are shown.