Radio-frequency optical double-resonance spectrum of SrF: The X2Σ + state

The isotropic and anisotropic hyperfine constants of the ground X²Σ ⁺ state of ⁸⁸SrF and ⁸⁶SrF are reported. Vibrational and rotational dependences are studied in a Dunham expansion analysis. Furthermore, the vibrational, rotational, and isotopic dependence of the spin-rotation constant is determined. The following values are obtained for X²Σ ⁺, v = 0, in ⁸⁸SrF: γ₀ = 74.79485 MHz, γ₁ = 5.752 × 10 ^-5MHz, γ₂ = -6.3 × 10 ^-10MHz, b₀ = 97.0834 MHz, b₁ = -3.300 × 10 ^-4MHz, c₀ = 30.268 MHz, C_I = 0.00230 MHz, where γ is the spin-rotation parameter, b and c are the Frosch and Foley hyperfine parameters, and C_I is a nuclear spin-rotation correction.