Efficient production of $^{229m}$Th via nuclear excitation by electron capture

TL;DR

This paper proposes a new theoretical method using nuclear excitation by electron capture (NEEC) to produce $^{229m}$Th efficiently, potentially increasing production rates by six orders of magnitude over previous methods, aiding nuclear clock development.

Contribution

The study introduces a novel NEEC-based approach for efficient $^{229m}$Th production, with detailed theoretical analysis and identification of experimental signatures.

Findings

Production rate can be six orders of magnitude higher than previous methods.

NEEC signatures can be unambiguously identified in experiments.

The approach offers a promising pathway for nuclear clock applications.

Abstract

The nuclear isomeric state $^{229m}$Th with an exceptionally low excitation energy makes the $^{229}$Th isotope a crucial candidate for nuclear clocks and many other applications. Efficient and controllable production of $^{229m}$Th is essential and still remains a challenge. Here we report a novel approach for efficient production of $^{229m}$Th by the excitation of $^{229}$Th to the above-lying excited state at $29.19$ keV energy via the process of nuclear excitation by electron capture (NEEC). We show theoretically that the production rate of $^{229m}$Th per nucleus with accessible conditions can be six orders of magnitude larger than the value experimentally demonstrated using $29$-keV synchrotron radiation for this indirect excitation. With the efficient production of $^{229m}$Th, our results identify scenarios, as well as the characteristic NEEC signature with which NEEC events could be unambiguously identified, for a clear experimental identification of the long-sought NEEC phenomenon.