Molecular-Beam Magnetic Resonance Studies of HD andD2

Abstract

The results of some recent molecular-beam magnetic resonance experiments on HD and ${\mathrm{D}}_{2}$ are reported. A discussion is given of the shifts and distortions of the separated oscillatory field resonance pattern produced by inhomogeneities in the external magnetic field and by the Bloch-Siegert effect. The sign of the electron-coupled spin-spin interaction constant in HD was remeasured to be positive. Its magnitude was determined to be 47(7) Hz. The spectrum of the $J=1$ state of ${\mathrm{D}}_{2}$ was observed for external fields less than 160 G, and the spin-rotation and second-rank tensor interaction constants were determined to be ${c}_{d}=+8.768(3)$ and $d=+25.2414(14)$ kHz. Using the calculated value ${d}_{M}^{\ensuremath{'}}=+2.737(1)$ kHz for the magnetic spin-spin interaction constant, the value of the electric quadrupole interaction constant was determined from the observed value $d$ to be $\frac{\mathrm{eqQ}}{h}=+225.044(24)$ kHz in the first rotational state of ${\mathrm{D}}_{2}$. Hyperfine transitions were observed for the first time in the second rotational state of ${\mathrm{D}}_{2}$. The hyperfine constants were determined from the transitions in the limit of zero external magnetic field to be ${c}_{d}=+8.723(20)$, ${d}_{M}^{\ensuremath{'}}=2.725(14)$, and $\frac{\mathrm{eqQ}}{h}=+223.38(18)$ kHz in the second rotational state. The effects of isotopic substitution and nuclear motion on the hyperfine constants in molecular hydrogen are discussed.