Sensitivity coefficients to $\alpha$-variation for fine-structure transitions in Carbon-like ions

TL;DR

This paper computes sensitivity coefficients for fine-structure transitions in Carbon-like ions, which are useful for detecting potential variations in the fine-structure constant over cosmological timescales, especially at high redshifts.

Contribution

It provides new calculations of sensitivity coefficients and isotope shifts for specific transitions in Carbon-like ions, aiding astrophysical tests of fundamental constant variations.

Findings

Sensitivity coefficients are significant for C I and decrease along the isoelectronic sequence.

Isotope shifts are substantial for C I but negligible for Mg VII and Si IX.

Transitions are observable at high redshifts, enabling cosmological studies.

Abstract

We calculate sensitivity coefficients to $\alpha$-variation for the fine-structure transitions (1,0) and (2,1) within $^3P_J[2s^2 2p^2]$ multiplet of the Carbon-like ions C I, N II, O III, Na VI, Mg VII, and Si IX. These transitions lie in the far infrared region and are in principle observable in astrophysics for high redshifts z~10. This makes them very promising candidates for the search for possible $\alpha$-variation on a cosmological timescale. In such studies one of the most dangerous sources of systematic errors is associated with isotope shifts. We calculate isotope shifts with the help of relativistic mass shift operator and show that it may be significant for C I, but rapidly decreases along the isoelectronic sequence and becomes very small for Mg VII and Si IX.