Pure Rotational Spectra of the Rare Isotopologues of TiO (X 3 Δ r ) Andrew P. Lincowski, DeWayne T. Halfen, and Lucy M. Ziurys Department of Chemistry and Biochemistry Department of Astronomy Steward Observatory Arizona Radio Observatory University of Arizona June 26, 2015

Why TiO Isotopologues? Chemical Aspect –Simple transition metal oxide – model for more complex species – 48 TiO most abundant isotopologue –High nuclear spin for 47 Ti (I = 5/2) and 49 Ti (I = 7/2) –Hyperfine structure – bonding characteristics (Kamiński et al. 2013) Astronomical Aspect –Metal oxides detected in stellar atmospheres for around 100 years – 48 TiO observed in atmosphere of M-type stars (e.g. Herbig 1948) – 48 TiO detected in circumstellar envelope red supergiant (RSG) star VY CMa (Kamiński et al. 2013)

(Wyckoff & Wehinger 1972) Titanium isotope data used to investigate nucleosynthesis in M-type and RSG stars 47 Ti, 48 Ti, and 49 Ti produced in silicon-burning 46 Ti created in oxygen- burning 50 Ti made in s-process TiO isotopologues observed in ο Ceti with enhanced 50 TiO (Wyckoff & Wehinger 1972)

(Chavez & Lambert 2009)

Past Studies of TiO Isotopologues Rotational spectrum of 48 TiO recorded by Namiki et al. (1998) Flechter et al. (1993) measured B 3  –X 3  r with LIF and PPMODR – 47 TiO hyperfine structure constants estimated A 3  –X 3  r (0,0) band measured by Barnes et al. (1996) showed partially resolved 47 TiO and 49 TiO hyperfine structure –Similar hf parameters for both isotopologues Kobayashi et al. (2002) observed the E 3  –X 3  r state for all five isotopologues Amiot et al. (2002) also recorded the B 3  –X 3  r (1-0) bands of all five isotopologues Flechter et al. (1993)

Energy Level Diagram for TiO (X 3  r ) 3  r ground state –Two unpaired 3d electrons –J = L + S Spin-orbit and spin-spin interactions Omega ladders –  = 1, 2, 3 – J ≥  Lambda-doubling possible Titanium hyperfine –I( 47 Ti)= 5/2 –I( 49 Ti)= 7/2 –F = J + I F J+3/2 J+1/2 J+7/2 J+5/2 J-5/2 J-7/2 J-1/2 J-3/2 J  X 3rX 3r 3

Millimeter-wave Direct Absorption Spectroscopy Gunn oscillator/Schottky diode multiplier frequency source ( GHz) Double walled steel reaction chamber which contains a Broida-type oven InSb hot electron bolometer Radiation is modulated at 25 kHz and detected at 2f; 2nd derivative spectrum

High Temp Gas Cell Detector Radiation Source

Gas-Phase Synthesis Metal vapor source: Broida oven –Liquid titanium (m.p. = 1668 o C) –Special thermal insulation needed –Slowly heated to 750 W Add N 2 O reactant gas –Over top of oven –Pressure: ~ 1 mtorr 30 mtorr Ar carrier gas added from below oven

Fourier Transform Millimeter-wave Spectroscopy Operates from 40 – 90 GHz TiO: J = 2 → 1 near 63 GHz E-band waveguide components Double 4 – 40 GHz synthesizer freq. Radiation coupled to cavity by circular hole in mirror Detected by MMIC LNA

Used Laser Ablation Source Nd/YAG laser at 532 nm Ablation adapter with Teflon nozzle Added 0.1% N 2 O in Ar No DC discharge needed Gas Phase Synthesis of TiO (X 3 Δ r ) Laser Beam Internal window Motor Housing Metal Rod Nozzle Pulsed Valve Ablation Adapter

Rotational Spectra of TiO (X 3 Δ r ) Isotopologues Work in progress Measured several transitions for 46 TiO, 47 TiO, 49 TiO, and 50 TiO with mm/submm spectrometer in natural abundance – 46 Ti (8.3 %), 47 Ti (7.4 %), 49 Ti (5.4 %), and 50 Ti (5.2 %) All three Ω ladders for all isotopologues Hyperfine splittings for 47 TiO (I = 5/2) and 49 TiO (I = 7/2) in submm range Hyperfine components of J = 2 → 1 for 47 TiO with FTmmW instrument near 63 GHz No lambda-doubling observed in J = 2 → 1 transition of 46 TiO, 47 TiO, 48 TiO, or 50 TiO

5000 shots

Frequency (GHz) * * + F =16.5 ← 15.5 F =11.5 ← 10.5 F =10.5 ← 9.5 F =17.5 ← 16.5 F =16.5 ← 15.5 F =11.5 ← 10.5 F =17.5 ← 16.5 F =10.5 ← 9.5 F =16.5 ← 15.5 F =11.5 ← 10.5 F =17.5 ← 16.5 F =10.5 ← 9.5 Interplay between a, b+c hf terms – h = aΛ + (b+c)Σ

F = 4.5 → shots

Preliminary Analysis of TiO (X 3 Δ r ) Isotopologues H eff = H rot + H so + H ss + H mhf Determined rotational, fine structure, and hyperfine constants Consistent with past optical studies Spectroscopic Constants for TiO Isotopologues (X 3 Δ r ) Parameter a46 TiO 47 TiO 49 TiO 50 TiO B (42) (37) (42) (28) D (94) (88) (99) (58)  b ADAD (39) (33) (38) λ b λDλD (95)0.0221(93)0.0172(51)0.0177(65) a-56.5(5.6)-72.5(5.0) b-259(24)-301(14) b+cb+c-214(25)-151(19) eQq rms a In MHz; errors are 3σ. b Held fixed to values of Namiki et al. (1998) Optical Work 47 TiO -54.7(6.3) -232(18) -49(93) a In MHz; 3  errors

First pure rotational spectrum of 46 TiO, 47 TiO, 49 TiO, and 50 TiO First hyperfine analysis of 49 TiO First full analysis of 46 TiO, 47 TiO, 49 TiO, and 50 TiO ground state Finish FTmmW spectrum of 47 TiO and 49 TiO near 63 GHz Astronomical observations with ALMA More Ti-containing species –Good method for Ti vapor generation Conclusions and Future Directions

Acknowledgements Prof. Lucy Ziurys Jie Min Julie Anderson John Keogh Deborah Schmidt Kyle Kilchenstein Andrew Lincowski NSF and NASA