Measurements yield precise atomic masses for nuclear reactions in the stars

Matter is composed of chemical elements mainly created in stars via nuclear reactions and complex nuclear reaction networks. To understand these processes, we need to know properties of participating nuclei, such as their masses. In her doctoral thesis in the field of nuclear physics at the University of Jyväskylä, M. Sc. Laetitia Canete has precisely measured the atomic masses of the radioactive isotope of six elements. The measurement data can be used to better model different astrophysical processes.

In the JYFL Accelerator Laboratory of the University of Jyväskylä, stable ion beams from the K-130 cyclotron are used to produce nuclei relevant for nuclear astrophysics by impinging them into a thin target foil at the IGISOL (Ion Guide Isotope Separator On-Line ) facility. The produced radioactive isotopes are transported into the JYFLTRAP double Penning trap mass spectrometer where their atomic mass values are determined with a precision of around 10 ppb. During her Ph.D., Laetitia Canete measured masses of six radioactive nuclei, ²⁵Al, ³⁰P, ³¹Cl, ⁶⁷Fe, ⁶⁹Co and ⁷⁰Co.

The measurements are relevant for various astrophysical problems. The production of the observed cosmic 1809-keV g-rays originating from ²⁶Al can be bypassed by proton captures on ²⁵Al. The proton-capture rate, and thus the amount of produced 1809-keV g-rays, is affected by the mass of ²⁵Al. The mass of ³⁰P is important for constraining the proton-capture rate on ³⁰P(p,g)³¹S controlling the production of elements heavier than sulphur in novae. The mass of ³¹Cl plays a role in type I X-ray bursts, and is also important for understanding fundamental properties of the nuclear force between protons and neutrons. The masses of ⁶⁷Fe, ⁶⁹Co and ⁷⁰Co play a role in the rapid neutron capture process producing around half of the elements heavier than iron.

Laetitia Canete completed her Master degree in subatomic physics and astrophysics at the University Lyon 1, France, in 2014. She entered at the Department of Physics of the University of Jyväskylä in summer 2014 and started her doctoral studies within the IGISOL group in the Accelerator Laboratory of the University of Jyväskylä.

The dissertation "High precision mass measurements for nuclear astrophysics"is published in JYU dissertations series, University of Jyväskylä, N:o. 64.