Microwave spectrum of the MnO radical in the X 6Σ+ state

Abstract

The microwave spectrum of MnO in the Σ+6 ground electronic state was detected using a source-modulated submillimeter-wave spectrometer. The MnO radical was efficiently generated by dc sputtering of manganese flakes placed inside a hollow cathode in the presence of an oxygen and helium mixture. In total, 283 spectral lines were measured in the frequency region of 210–450 GHz for nine rotational transitions, each of which showed six fine structure line groups consisting of several hyperfine structure components due to the Mn55 nucleus (I=5/2). A least-squares analysis of the measured line frequencies resulted in the determination of rotational, fine, and hyperfine coupling constants including higher-order spin–orbit distortion terms for the spin–spin, spin–rotation interactions and the Fermi contact interaction of the Mn nucleus. The hyperfine coupling constants were used to assess plausible molecular orbital bonding models.

The Pure Rotational Spectra of TiO(X3Δ) and TiN(X2Σ+)

“…The more common generation scheme of sputtering the transition metal from the metal electrode has been used in the study of CuO (28), MnO (29), and AgO (30). An attempt to observe the rotational transitions of TiN and TiO by sputtering a titanium hollow cathode in the presence of a He/N 2 or He/O 2 mixture revealed no detectable signal even upon averaging 1000 scans.…”

Molecules in high spin states II: the pure rotational spectrum of MnF (X7Σ+)

“…Centrifugal distortion corrections to c, as well as higher order terms such as h; c s , and b s , were used in the initial analyses but could not be defined. In contrast, c D ; c s ; h; and b F D were all found to be necessary to fit MnS [11] and MnO [10] in their X 6 R þ states.…”

“…For example, the spin-spin constant is near 10 GHz in MnS and 17 GHz in MnO, while in MnF it is )136.5 MHztwo orders of magnitude smaller. The spin-rotation constant is smaller by a factor of 4 in the fluoride relative to the sulfide and oxide as well, which both have c ' À71 MHz [10,11]. Hence, higher order terms may be sufficiently small such that they are not needed for MnF.…”

“…As shown in Table 4, b F falls in the range from 206.5 MHz for MnS [11] to 479.9 MHz in MnO [10]. The dipolar c constant is correspondingly small.…”

“…The hyperfine Chemical Physics Letters 380 (2003) 632-646 www.elsevier.com/locate/cplett interactions in MnH have in fact been found to be so substantial that they cause mixing of the seven spin components, destroying the ÔgoodnessÕ of the J quantum number [9]. Pure rotational spectra have also been recorded for MnO [10] and MnS [11], as well, in their X 6 R þ ground states. In both cases, higher order fine and hyperfine constants were found necessary to fully analyze these problematic data sets.…”