Electron Paramagnetic Resonance Spectrum of O2(1Δg)—Its 17O Hyperfine Coupling and Electronic and Rotational g Values

Abstract

The 17O hyperfine coupling was measured for O2(1Δg) in its J = 2 angular momentum state. The coupling constant 2gIμNμB〈Σilzi / ri3〉 was measured to be − 424 ± 1 MHz. From this value we can follow Harvey's convention and determine 〈1 / rl3〉 = 39.6 × 10−24cm−3. The previous work by Miller et al. on O2(3Σg−) can be used to determine 〈1 / rs3〉 = 43.6 × 10−24cm−3. Even though these two values refer to different electronic states, they are in the same ratio that Harvey found for O(3P), but they are both appreciably larger than the values he found for O(3P). The gJ values were determined for both the J = 2 and J = 3 angular momentum states. From these values we obtain gL = 0.999860 and gr = − 1.70 × 10−4. The gL value is very close to the recent determination of Miller, but the gr value does not agree with Miller's work.

Hyperfine structure of the transitions of 16O17O, 17O18O and 17O2 by CRDS at 80K

“…Our spectra (Figure 1 for instance) show that the observed hf splitting is significantly larger than the Doppler broadening and then that the hf structure of the a 1 D g upper state is larger than that of the ground state. This is consistent with earlier EPR measurements of 16 [4]. The general expression of the hyperfine structure Hamiltonian can be written as…”

“…To the best of our knowledge, the only previous determination of the hf coupling constant in the a 1 D g state is due to Arrington et al [4] who obtained the a value of 16 [4]. Since in theory there is no isotopic dependence for this parameter, they performed a global fit for the two species and determined the coupling constant to be À424 ± 1 MHz which is almost exactly a factor of two greater than our values (À217.3 ± 1.9 and À211.5 ± 2.6 MHz, for 16 We have superimposed to the spectra of Figures 2 and 3 a simulation of the hf structure calculated with the fitted parameters values.…”

“…The hf coupling parameters of the X 3 + À g and a 1 D g states of 16 [4], there is a factor of 2 in the a parameter due to a different definition.…”

“…Indeed, unlike other isotopes of oxygen 17 O has a non-zero nuclear spin (I = 5/2) and the coupling of the nuclear spin to electron spin in the X 3 + À g state [3] and to the electronic angular momentum in the a 1 D g state [4] gives rise to a magnetic hyperfine (hf) structure. As a result of the Doppler broadening at room temperature, the magnetic hyperfine structure could not be resolved and it manifested itself only as a broadening of the 16 The present study is devoted to a detailed experimental investigation of the hf structure of the 17 O containing isotopologues of oxygen, on the basis of new CRDS spectra of the a 1 D g À X 3 + À g band recorded at room temperature and at liquid nitrogen temperature (about 80 K, see below).…”

“…The coupling parameters will be determined and compared to the values available in the literature [4].…”