The Rotational Spectrum of TiO₂

Abstract

The rotational spectrum of titanium dioxide (TiO 2 ) has been detected by laser-ablation molecular beam Fourier transform microwave spectroscopy. Thirteen b-type rotational transitions up to J ¼ 9 and K a ¼ 4 were measured for the most abundant isotopic species 48 TiO 2 in the frequency range 7Y42 GHz with accuracies of 1Y10 kHz, allowing for the precise determination of rotational and centrifugal distortion parameters. In addition, eight and six rotational transitions of the rare isotopic species 46 TiO 2 and 50 TiO 2 , respectively, have been recorded in the same frequency range. From the derived spectroscopic parameters, rest frequencies of TiO 2 can now be calculated to better than 1 km s À1 in equivalent radial velocity up to fairly high J and K a at millimeter wavelengths, enabling radioastronomical searches for this stable, highly polar transition metal dioxide in space. Preliminary results of two searches for TiO 2 in space are presented.

Pure rotational spectra of TiO and TiO2in VY Canis Majoris

“…Radio astronomers had long sought TiO in the interstellar medium and circumstellar environments (Churchwell et al 1980;Millar et al 1987;Brünken et al 2008), because observations of its rotational lines might yield the temperature and abundances more directly than at optical wavelengths. Although there have been several attempts to observe TiO at radio wavelengths (most with single antennas), all were unsuccessful.…”

“…The rotational spectrum of TiO 2 was first observed in the laboratory when Brünken et al (2008) measured 13 transitions to high accuracy in the centimeter band. Brünken et al determined the rotational and leading centrifugal distortion constants that allow predictions of the astronomically important transitions in the millimeter and submillimeter bands, which subsequent measurements confirmed are accurate to 0.5 km s −1 or better (Kania et al 2011).…”

Communication: A vibrational study of titanium dioxide cation using the vacuum ultraviolet laser pulsed field ionization-photoelectron method

“…Despite the recognized importance of TiO 2 in many research fields, only a few spectroscopic studies on TiO 2 have been reported. 9,10 These spectroscopic studies have provided accurate rotational and vibrational constants and thus geometric parameters for the TiO 2 (X 1 A 1 ) ground state. 9,10 On the theoretical side, predictions on the IE, dissociation energies, molecular geometry, and harmonic vibrational frequencies for TiO 2 (X 1 A 1 ) have also been reported.…”

“…9,10 These spectroscopic studies have provided accurate rotational and vibrational constants and thus geometric parameters for the TiO 2 (X 1 A 1 ) ground state. 9,10 On the theoretical side, predictions on the IE, dissociation energies, molecular geometry, and harmonic vibrational frequencies for TiO 2 (X 1 A 1 ) have also been reported. [11][12][13] However, up to the present no spectroscopic studies on the TiO 2 + cation have been made, and thus the IE(TiO 2 ) and harmonic vibrational frequencies for TiO 2 + are not known.…”

“…3b • . 9 The DFT calculation of Grein 13 . Taking into account the vibrational symmetry rule along with the anti-bonding character of the HOMO, we have assigned the observed PFI-PE bands to members of three PFI-PE vibrational progressions:…”