The pure rotational spectrum of ZnBr (X 2 Σ + ) has been recorded in the frequency range 259-310 GHz using millimeter-wave direct absorption techniques. This study is the first quantitative spectroscopic investigation of this free radical. ZnBr was synthesized in a DC discharge by the reaction of zinc vapor in argon with one of three reagents: BrCH 3 , Br 2 CH 2 , or Br 2 . Eight rotational transitions were measured for six isotopologues ( 64 Zn 79 Br, 64 Zn 81 Br, 66 Zn 79 Br, 66 Zn 81 Br, 68 Zn 79 Br, and 68 Zn 81 Br), all of which exhibited spin-rotation interactions. Furthermore, transitions originating in the v = 1 through 3 excited vibrational states were obtained for certain isotopologues. Five rotational transitions were also recorded for 67 Zn 79 Br, in which hyperfine splittings were observed arising from the 67 Zn nucleus (I = 5/2). The spectra were analyzed using a Hund's case (b βJ ) Hamiltonian, and rotational, spin-rotation, and 67 Zn magnetic hyperfine constants were determined. Equilibrium parameters were also derived for the 64 Zn 79 Br, 64 Zn 81 Br, 66 Zn 79 Br, and 66 Zn 81 Br isotopologues, including the vibrational constant, ω e = 286 cm -1 . The equilibrium bond length was derived to be r e = 2.268 48(90) Å. Analysis of the 67 Zn hyperfine parameters suggest a decrease in ionic character in ZnBr from the other known zinc halides, ZnF and ZnCl.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry