Metastable a 3Π 13CO: Molecular-Beam Electric-Resonance Measurements of the Fine Structure, Hyperfine Structure, and Dipole Moment

Abstract

The radio-frequency spectrum of metastable a 3Π 13CO has been measured in molecular-beam electric resonance in the range 0–2000 MHz. Electric-dipole transitions with ΔJ = 0 and ΔF = 0, ± 1 have been observed in states | υ, Ω, J, F〉 = | 0–3, 1–2, 1–7, J ± 12〉 at zero field. The set of transitions in each vibrational state has been analyzed to give three parameters describing the lowest-order magnetic hyperfine interactions of the 13C nuclear spin (I = 12) with the spin (S) and orbital (L) angular momenta of the two unpaired electrons in the 5σ2π open-shell configuration. The vibrational dependence of the measured hyperfine parameters is fitted to a polynomial in (υ + 12)n to give: OriginParameterValue at Re(a 3π) (in MHz)I·SFermi contactK=1935.1 ± 0.5I·Sspin–spin dipoleDδ=106.5 ± 0.1D=7.9 ± 0.1I·Lspin–orbitalG=162.5 ± 0.1 Restricted Hartree–Fock calculations of these hyperfine terms are in good agreement with the measured values. The Stark effect has been measured in states | υ, Ω, J, F〉 = | 0–3, 2, 2–3, J + 12〉 of a 3Π 13CO to give dipole moments which display a slight nonvibrational isotopic shift (1 in 104) from the moments measured in the corresponding states | υ, Ω, J〉 of a 3Π 12CO.

UV-frequency metrology on CO (a3Π): Isotope effects and sensitivity to a variation of the proton-to-electron mass ratio

“…We have included the hyperfine interaction in the effective Hamiltonian following Brown et al [29]. Only terms that are diagonal in J were included, since contributions from off-diagonal terms are estimated to be smaller than 100 kHz [11]. We have fitted our optical data simultaneously with lambda-doublet transition frequencies measured by Gammon et al [11] and the rotational transition frequencies measured by Saykally et al [4].…”

“…Only terms that are diagonal in J were included, since contributions from off-diagonal terms are estimated to be smaller than 100 kHz [11]. We have fitted our optical data simultaneously with lambda-doublet transition frequencies measured by Gammon et al [11] and the rotational transition frequencies measured by Saykally et al [4]. The fitted set consisted of 19 rf transitions, 4 mw transitions and 24 optical transitions.…”

Testing the mass-scaling relations in the a3Π state of 12C18O and 13C16O

“…[14,15]. Briefly, commercial isotopically-enriched gases (Sigma Aldrich, 12 C 18 O purity $95%, and 13 C…”

“…Extensive studies on the a 3 P state of 12 C 16 O have been performed in radio-frequency, microwave, infrared, optical and UV studies [2][3][4][5][6][7][8][9][10][11]. Also, 13 C 16 O and 12 C 18 O have been studied using rf, mw and UV spectroscopy [4,11,12]. Recently, rotational transitions in metastable CO in its a 3 P state have been identified as a sensitive probe to detect a possible time-variation of the proton-to-electron mass ratio, l, on a laboratory time scale [13].…”

Ramsey-type microwave spectroscopy on CO (a3Π)

“…The transitions connecting the a 3 Π state to the X 1 Σ + ground state were first observed by Cameron in 1926 [21]. Later, the a 3 Π state was studied using radio frequency [22][23][24], microwave [25][26][27], infrared [28,29], optical [30] and UV spectroscopy [31]. We have recently measured selected transitions in the CO a 3 Π -X 1 Σ + (0-0) band using a narrow-band UV laser [20] resulting in a set of molecular constants that describes the level structure of the a 3 Π state with an absolute accuracy of 5 MHz with respect to the ground state and a relative accuracy of 500 kHz within the a 3 Π state.…”