In-flight production of an isomeric beam of $^{16}$N

TL;DR

This study demonstrates the in-flight production of an $^{16}$N beam with a significant isomeric component using inverse kinematics reactions at an upgraded accelerator, providing insights into isomer yields and reaction dynamics.

Contribution

First in-flight production and measurement of an $^{16}$N isomeric beam using inverse kinematics at ATLAS, with detailed analysis of isomer fractions and reaction energy dependence.

Findings

40(5)% isomeric state at 7.9 MeV/u

24(2)% isomeric state at 13.2 MeV/u

Reaction energy and angular acceptance significantly affect isomer yield

Abstract

An in-flight beam of $^{16}$N was produced via the single-neutron adding ($d$,$p$) reaction in inverse kinematics at the recently upgraded Argonne Tandem Linear Accelerator System (ATLAS) in-flight system. The amount of the $^{16}$N beam which resided in its excited 0.120-MeV $J^{\pi}=0^-$ isomeric state (T$_{1/2}\approx5$ $\mu$s) was determined to be 40(5)% at a reaction energy of 7.9(3) MeV/$u$, and 24(2)% at a reaction energy of 13.2(2) MeV/$u$. The isomer measurements took place at an experimental station $\approx30$ m downstream of the production target and utilized an Al beam-stopping foil and a HPGe Clover detector. Composite $^{16}$N beam rate determinations were made at the experimental station and the focal plane of the Argonne in-flight radioactive ion-beam separator (RAISOR) with Si $\Delta$E-E telescopes. A Distorted Wave Born Approximation (DWBA) approach was coupled with the known spectroscopic information on $^{16}$N in order to estimate the relative $^{16}$N isomer yields and composite $^{16}$N beam rates. In addition to the observed reaction-energy dependence of the isomer fraction, a large sensitivity to angular acceptance of the recoils was also observed.