Knowledge Bank

We have measured radiofrequency transitions between h'{i}s levels in the $J=2$ and $J=3$ states of TlBr. The measurements were made with a molecular beam electric resonance $spectrometer1$ under conditions of very weak electric and magnetic fields. From the observed frequencies we have calculated the hyperfine interaction constants for the ground vibrational state of $\mathrm{<mrow\; data-mjx-texclass="ORD">205</mrow>}Tl79Br$ and $\mathrm{<mrow\; data-mjx-texclass="ORD">205</mrow>}Tl81Br$. These are; $\mathrm{<mrow\; data-mjx-texclass="ORD">205</mrow>}T\ell 79Br\mathrm{<mrow\; data-mjx-texclass="ORD">205</mrow>}T\ell 81BreqQBr126.31\pm 0.1105.52\pm 0.1MHzcBr3.72\pm 0.53.96\pm 0.5kHzcTI42.75\pm 0.542.57\pm 0.5kHzc3-1.59\pm 2.0-1.74\pm 2.0kHzc4-6.37\pm 2.0-7.23\pm 2.0kHz$ where $eqQBr$ is the quadrupole coupling constant for the bromine nucleus, $CBr$ and $CTl$ are the spin-rotation coupling constants for the bromine and thallium nuclei, respectively, and $C3$ and $C4$ are the coupling constants for the tensor and scalar parts of the nuclear spin-spin interaction. The values of $eqQBr$ are in agreement with, but more precise than those obtained by $Fitzky2$ with microwave absorption spectroscopy. The magnetic coupling constant had not been measured previously. Measurements are being continued on the $J=1$ and $J>3$ states, the excited vibrational states, and on the accompanying lines for the $\mathrm{<mrow\; data-mjx-texclass="ORD">203</mrow>}Tl$ isotope. Work of the same nature is being done on TlI, but analysis of the observed spectrum is still in progress.