Gravitational Wave Effects on Radio Spectral Lines of Atomic Hydrogen: Hyperfine Splitting and Broadening Mechanisms
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arXiv
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| Format: | Preprint |
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2025
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| author | Wanwieng, Nontapat Thaicharoen, Nithiwadee Chattrapiban, Narupon Watcharangkool, Apimook |
| author_facet | Wanwieng, Nontapat Thaicharoen, Nithiwadee Chattrapiban, Narupon Watcharangkool, Apimook |
| contents | We explore the effects of gravitational waves (GWs) on hydrogen's radio spectral lines, focusing on the ground-state hyperfine transition and radiative transitions in highly excited Rydberg states. To analyze GW impacts on hyperfine structure, we derive Maxwell's equations in a gravitational-wave background using linearized gravity and the $3+1$ formalism. Our findings reveal that GWs induce energy shifts in hyperfine magnetic substates, modifying the 21 cm line. However, these energy shifts fall well below the detection limits of current radio astronomical instruments. For transitions in highly excited states, which produce radio recombination lines (RRL), the influence of GW manifests itself as spectral broadening, with the fractional linewidth for $\mathrm{H}nα$ scaling as $Δν/ν_0 \sim n^7ω^2_{\mathrm{gw}}h(t)$. This suggests that RRLs could serve as probes for ultra-high-frequency GWs, particularly given that Rydberg atoms in the interstellar medium can reach quantum numbers above $n=100$. As an example of possibly detectable high frequency GW source, We investigate GWs emitted during the inspiral of planetary-mass primordial black hole binaries, where GW-induced broadening in RRLs could exceed natural broadening effects. Additionally, we examine the influence of the recently detected stochastic gravitational-wave background on hydrogen spectral lines. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_13118 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Gravitational Wave Effects on Radio Spectral Lines of Atomic Hydrogen: Hyperfine Splitting and Broadening Mechanisms Wanwieng, Nontapat Thaicharoen, Nithiwadee Chattrapiban, Narupon Watcharangkool, Apimook General Relativity and Quantum Cosmology High Energy Astrophysical Phenomena Quantum Physics We explore the effects of gravitational waves (GWs) on hydrogen's radio spectral lines, focusing on the ground-state hyperfine transition and radiative transitions in highly excited Rydberg states. To analyze GW impacts on hyperfine structure, we derive Maxwell's equations in a gravitational-wave background using linearized gravity and the $3+1$ formalism. Our findings reveal that GWs induce energy shifts in hyperfine magnetic substates, modifying the 21 cm line. However, these energy shifts fall well below the detection limits of current radio astronomical instruments. For transitions in highly excited states, which produce radio recombination lines (RRL), the influence of GW manifests itself as spectral broadening, with the fractional linewidth for $\mathrm{H}nα$ scaling as $Δν/ν_0 \sim n^7ω^2_{\mathrm{gw}}h(t)$. This suggests that RRLs could serve as probes for ultra-high-frequency GWs, particularly given that Rydberg atoms in the interstellar medium can reach quantum numbers above $n=100$. As an example of possibly detectable high frequency GW source, We investigate GWs emitted during the inspiral of planetary-mass primordial black hole binaries, where GW-induced broadening in RRLs could exceed natural broadening effects. Additionally, we examine the influence of the recently detected stochastic gravitational-wave background on hydrogen spectral lines. |
| title | Gravitational Wave Effects on Radio Spectral Lines of Atomic Hydrogen: Hyperfine Splitting and Broadening Mechanisms |
| topic | General Relativity and Quantum Cosmology High Energy Astrophysical Phenomena Quantum Physics |
| url | https://arxiv.org/abs/2503.13118 |