Mass-independent analysis of the stable isotopologues of gas-phase titanium monoxide – TiO

Abstract

More than 130 pure rotational transitions of 46 TiO, 47 TiO, 48 TiO, 49 TiO, 50 TiO, and 48 Ti 18 O are recorded using a high-resolution mm-wave supersonic jet spectrometer in combination with a laser ablation source. For the first time a mass-independent Dunham-like analysis is performed encompassing rare titanium monoxide isotopologues, and are compared to results from high-accuracy quantum-chemical calculations. The obtained parametrization reveals for titanium monoxide effects due to deviations from the Born-Oppenheimer approximation. Additionally, the dominant titanium properties enable an insight into the electronic structure of TiO by analyzing its hyperfine interactions. Further, based on the mass-independent analysis, the frequency positions of the pure rotational transitions of the short lived rare isotopologue 44 TiO are predicted with high accuracy, i.e., on a sub-MHz uncertainty level. This allows for dedicated radio-astronomical searches of this species in core-collapse environments of supernovae.

The rotationally resolved infrared spectrum of TiO and its isotopologues

“…Molecular parameters of TiO were derived from a global data set analysis using high-resolution data from Breier et al (2019) and the here presented mid-IR measurements on multi-isotopologue ro-vibrational TiO transitions. The mass-independent molecular parameterization is described in detail by Breier et al (2018Breier et al ( , 2019. In short, the parameter description of TiO is obtained by an adjustment procedure of the following isotopically invariant equation of the molecular parameters, The isotopic invariant Dunham-like fitting parameterÔ k,l takes a central role in Equation 1.…”

“…For hyperfine parameters, η is set to be the nuclear g N -factor for magnetic hyperfine parameters and the electric hyperfine parameters are scaled by the electric quadrupole moment Q, respectively. The scaling values of TiO are given in Breier et al (2019). The isotopic invariance is introduced into Equation 1 by the reduced mass µ α .…”

“…The generalized equation is implemented in the program PGOPHER (Western 2017). Contrary to Breier et al (2019), the weighting process of the various data sets is changed and the well-defined iterative re-weighting procedure introduced by Watson ( 2003) is used to improve the reproducibility. The ROBUST parameter value of PGOPHER was determined to be 0.1.…”

“…Two sets of parameters are obtained by excluding ("Fit A") and including ("Fit B ") the spin-rotation interaction in the electronic ground state (see Table 2). In a global fit, the infrared data obtained in this work are combined with data for 46−50 Ti 16 O and 48 Ti 18 O at optical and microwave frequencies from the literature (Breier et al 2019;Lincowski et al 2016;Fletcher et al 1993;Ram et al 1999;Amiot et al 1995). A 00 × 10 −1 5.801031( 10 values are given in cm −1 .…”

“…Lincowski et al (2016) also obtained rotational constants, including centrifugal distortion constants for spin-spin and spin-orbit parameters, for all stable titanium isotopologues. Breier et al (2019) conducted measurements for all stable titanium isotopologues of TiO around 300 GHz. The data were analyzed using a mass-independent Dunham approach, which allows to investigate all isotopologues in a global fit, thus combining measurements at microwave and optical wavelengths.…”