SPECTROSCOPY OF Si O AND Si O IN

SPECTROSCOPY OF Si. O AND Si. O+ IN SUPPORT OF ULTRACOLD MOLECULE STUDIES IVAN ANTONOV, PATRICK STOLLENWERK, SRUTHI VENKATARAMANABABU, BRIAN ODOM ISMS 2018

WHAT AND WHY WE STUDY Cold (diatomic) molecular ions Fundamental constants time variation Cold chemistry experiments Scientific curiosity – molecular ions are poorly studied compared to neutrals Technique and instrument development Important questions How to prepare and trap the molecular ions How to retain the ions in the trap and manipulate their quantum states How to probe the nature and quantum state of the ions

HOW WE STUDY COLD IONS PMT Si. O REMPI Excitation Frequency Sweep CEM r 0 = 3 mm -3 k. V z 0 = 7. 3 mm Si. O+ Trapping RF ΩRF = 2π · 3. 6 MHz spectroscopy V RF < 650 VPP EC’s = <10 VDC

Si. O+ PREPARATION AND TRAPPING 6 -0 5 -0 9 -2 Si. O+ X 2Σ+ N A 1Π, v = 5 J” ~ + Si. O X 1ΣX 1 Σ+ 7 -1 6 -1(*) X 2Σ+, v = 0 J’ 11. 594 Si. O A 1(5) Π e. V Trot=Tvib=~1000 K X 1Σ+, v = 0 8 -2

Si. O+ PROBING Lifetime required τrot ≥ 5 ps τvib ≥ 5 fs 22Π state: Te = ~44500 cm-1 – 225 nm Re = 1. 58 Å, ωe = 913 -985 cm-1 Hdiss ~ 1500 -2000 cm-1 τX = 78 ns, τA = 4. 5 μs, τB = 12. 6 μs Other candidates: 32Π 42Π 32Σ+ much higher or have poor FCF overlap Δ and Σ- states only work for the A state probing Never observed before (for a good reason!) * Z. -L. Cai, J. P. Francois, J. Mol. Spec. , 197, 12 -18

Si. O+ PROBING Si. O+ 0 -0 ωe = 1053 (14) cm-1 Si+ωeχe = 29 (3) cm-1 22Π 1/2: Te = 43675 (12) cm-1 22Π 3/2: Te = 43492 (12) cm-1 B 0, B 1~=0. 7 cm-1, B 2 , B 3 < 0. 7 cm-1 1 -0 3 -0 2 -0

Si. O+ 22Π TRANSITION: COMPARISON TO THEORY Level Te, cm-1 ωeχe, cm-1 B, cm-1 Re , Å Current work Experiment 43583 1053 29 ~0. 7 cm-1 ~1. 54 Cai et al 1999 CMRCI/cc-p. VQZ 44680 913. 2 15. 13 0. 66698 1. 575 Das et al 2003 MRDCI/[7 s 6 p 5 d 2 f] PP for core electrons 44371 917 ~ ~ 1. 604 Shi et al 2012 44469 985 8. 1235 0. 66773 1. 5768 MRCI+Q/AV 6 Z+CV+DK

CONCLUSIONS Si. O 1+1 REMPI spectrum of Si. O A-X transition is recorded; Si. O IP is 11. 594(5) e. V 5 -0 A-X band is efficient for trap loading Si. O+ We found 22Π state of Si. O+ (C 2Π? ) The state predissociates on all observed vibrational levels The state will be used as vibrational, possibly rotational probe for Si. O+ (stay tuned for future results) Method In situ LCF-MS was used to study spectroscopy (and kinetics) of Si. O+ in ion trap LCF-MS is mass-selective and very sensitive to trapped molecules Using RF excitation sweeps allows faster data collection necessary for spectral and kinetic studies

THANK YOU! Our Group! PI Grad Students Brian Odom Pat Stollenwerk Sruthi Venkataramanababu Mark Kokish Qiming Wu James Dragan Panpan Huang Joseph Cordero-Mercado Gregorio Rabelo Moreira Da Silva Undergrads Chandler Conn Scott Carmichael Funding Agencies:

Si. O+ 22Π TRANSITION: COMPARISON TO THEORY 5. 47 5. 31 e. V Si 3 s 23 p 2 3 P + O+ 2 s 22 p 3 4 S○ Si+ 3 s 3 p 2 4 P + O 2 s 22 p 4 3 P 4. 19 e. V Si+ 3 s 23 p 2 P○ + O 2 s 22 p 4 1 S 1. 97 e. V Si+ 3 s 23 p 2 P○ + O 2 s 22 p 4 1 D Σ+ , Π 2Σ+, Σ- 3Π, 2Δ, Φ 2Σ+, 2Π 0 Si+ 3 s 23 p 2 P○ + O 2 s 22 p 4 3 P Σ+, 2Σ- 2Π, Δ