June 25, th International Symposium on Molecular Spectroscopy Hyperfine Resolved Pure Rotational Spectroscopy of ScN, YN, and BaNH (X 1  + ): Insight into Metal – Nitrogen Bonding Lindsay N. Zack, Matthew P. Bucchino, Justin Young, Marshall Binns, Phillip M. Sheridan, and Lucy M. Ziurys Department of Chemistry and Biochemistry, University of Arizona Department of Chemistry and Biochemistry, Canisius College

June 25, th International Symposium on Molecular Spectroscopy Previous Work ScN – Experimental: Ram and Bernath: FT emission spectroscopy A 1  + –X 1  + (  v = 0); Equilibrium rotational parameters Nakhate and Mukund: Jet-cooled LIF; B1, C1, D1 and a 3  + states (  v ≠ 0); rotational constants and fundamental vibrational frequencies – Computational: 1  + ground state Daoudi and coworkers: CIPSI, Sc–N double bond diradical Kunze & Harrison: MC-SCF, highly ionic Sc–N triple bond

June 25, th International Symposium on Molecular Spectroscopy Previous Work YN – Experimental: Ram & Bernath: FT emission spectroscopy A 1  + –X 1  + (  v = 0); Equilibrium rotational parameters Jakubek et al.: Jet-cooled LIF; B1, C1, D1 and a 3  + states (  v ≠ 0); rotational constants and fundamental vibrational frequencies – Computational: 1  + ground state Shim & Gingerich: CASSCF, Y–N double bond

June 25, th International Symposium on Molecular Spectroscopy Previous Work BaNH – Experimental: Janczyk and Ziurys: MM-wave: 138 BaNH, 137 BaNH, 138 BaND, and 138 BaND; r 0, r s, and r m (1) ; – Computational: 1  + ground state Linear; DFT: Ba – N triple bond, not purely ionic No experimental M or N hyperfine parameters for ScN, YN and BaNH

June 25, th International Symposium on Molecular Spectroscopy Fourier Transform Microwave Spectrometer 4 – 60 GHz Cyropumped vacuum chamber Fabry-Perot cavity Supersonic jet 40°relative to mirror axis 600 kHz scan increments Ziurys Laboratory FTMW

June 25, th International Symposium on Molecular Spectroscopy Discharge Assisted Laser Ablation (DALAS) Ablation laser: Nd:YAG (532nm, 200 mJ per pulse; 10 Hz rep rate; 990  s delay) DC discharge 1250 V (Y, Sc) or 1000 V (Ba) Metal vapor reacted with 0.2% 14 NH 3 or 15 NH 3 in Ar Ba Rod

Frequency (MHz) F 1 = 2.5 → 3.5F 1 = 4.5 → 3.5F 1 = 3.5 → 3.5 F = 2 → 3 F = 5 → 4 F = 4 → 3 F = 4 → 4 ScN (X 1 Σ + ): J = 1 → 0 F = 4 → 3 F = 4 → 4 F = 3 → 3 F = 3 → 4 F = 2.5 → 2.5 F = 2.5 → 3.5 F = 3.5 → 2.5 F = 3.5 → 3.5 F = 3.5 → 4.5 F = 1.5 → 2.5 F = 4.5 → 3.5 F = 4.5 → 4.5 F = 3.5 → 2.5 F = 3.5 → 3.5 F = 3.5 → 4.5 F = 5.5 → 4.5 F = 4.5 → 3.5 F = 4.5 → 4.5 F = 2.5 → 2.5 F = 2.5 → 3.5 F = 3.5 → 2.5 F = 3.5 → 3.5 F = 3.5 → 4.5 Sc 14 N Sc 15 N F = 3 → 3 F = 3 → 4 F 1 = J + I Sc F = F 1 + I N

Frequency (MHz) YN (X 1 Σ + ): J = 1 → 0 F 1 = 1 → 1 F = 1.5 → 0.5 F = 1.5 → 1.5 F 1 = 1 → 1 F = 0.5 → 0.5 F = 0.5 → 1.5 F 1 = 2 → 1 F = 2.5 → 1.5 F 1 = 2 → 1 F = 1.5 → 0.5 F = 1.5 → 1.5 F 1 = 0 → 1 F = 0.5 → 0.5 F = 0.5 → 1.5 F 1 = 1.5 → 0.5 F = 2 → 1 F 1 = 1.5 → 0.5 F = 1 → 0 F = 1 → 1 F 1 = 0.5 → 0.5 F = 1 → 0 F = 1 → 1 F 1 = 0.5 → 0.5 F = 0 → 1 Y 14 N Y 15 N F 1 = J + I N F = F 1 + I Y Also J = 2 → 1

138 Ba 14 NH (X 1 Σ + ): J = 1 → 0 Frequency (MHz) F = 1 → 1 F = 2 → 1 F = 0 → 1 ~ F = J + I N I N = 1

June 25, th International Symposium on Molecular Spectroscopy DFT Calculations Used to estimate hyperfine parameters (in MHz) Order of magnitude agreement between basis sets MoleculeBasis SeteQq (M)C I (M)eQq (N)C I (N) Sc 14 Naug-cc-pVTZ aug-cc-pVTZ (N)/LANL2DZ (M) SDD exp Sc 15 Naug-cc-pVTZ aug-cc-pVTZ (N)/LANL2DZ (M) SDD exp Y 14 Naug-cc-pVTZ (N)/LANL2DZ (M) SDD exp Y 15 Naug-cc-pVTZ (N)/LANL2DZ (M) SDD exp BaNHSDD exp 0.039

June 25, th International Symposium on Molecular Spectroscopy Sc 14 N Sc 15 NY 14 N Y 15 NBaNH B (10) (23) (14) (32) (17) (27) (18) (29) D (39) (13) (20)0.0186(13) (11) (19) H -5.4(1.9) x L 1.98(94) x eQq(M)33.818(19) (30) C I (M) (63) (77)-7.6(5.7) x (3.8) x eQq(N)-0.127(19) (10) 0.039(11) C I (N)7.3(3.0) x (6.1) x (2.3) x (3.1) x rms0.001 < Constants (MHz) Previous work BaNH: Combined fit with mm-wave data Experimental signs of eQq and C I match DFT and experimental intensities for BaNH

June 25, th International Symposium on Molecular Spectroscopy Nuclear Spin – Rotation: Sc and Y C I scales as g I × B (pairs of isotopologues) Molecule (Nucleus) ScN (Sc) ScN (N) YN (Y)1.1 YN (N)

June 25, th International Symposium on Molecular Spectroscopy ScF and ScO: –  HOMO 4s atomic Sc – remove 1 e - from ScF to ScO, no change in eQq (Sc) expected ScN: – Remove 1e- from ScO to ScN, no change in eQq (Sc) expected if similar electronic structure – Dramatic decrease in eQq (Sc) in ScN indicates different atomic orbital contribution to MO’s compared to ScF and ScO Scandium Electric Quadrupole MoleculeeQq (MHz) ScF74.086(15) ScO72.240(15) ScN33.818(19)  HOMO

June 25, th International Symposium on Molecular Spectroscopy Nitrogen Electric Quadrupole MoleculeeQq (MHz) ScN-0.127(19) TiN-1.515(19) CrN-2.080(27) YN (50) MoN-2.31(17) BaNH0.039(11) ScN, YN, BaNH: most ionic Townes-Dailey analysis sp hybridized N (Novick, JMS (2011)) – Estimate eQq (N) from atomic orbital populations – ScN (Kunze and Harrison): n hyb = 3.01, n px = n py =1.27; eQq(N) = MHz – ScN (Daoudi et al.): n hyb = 2.63, n px = n py =1.29; eQq(N) = MHz – eQq(N) supports Sc – N double bond diradical bond description of Daoudi et al. with considerable covalent character (calculated charge on N = -0.22)

June 25, th International Symposium on Molecular Spectroscopy Nitrogen Electric Quadrupole MoleculeeQq (MHz) ScN-0.127(19) TiN-1.515(19) CrN-2.080(27) YN (50) MoN-2.31(17) BaNH0.039(11) – YN (Shim and Gingerich): AO populations  eQq(N) = MHz – Calculated charge on N = -0.61; unlikely increase in charge compared to ScN – Investigate YN using computational methods of Daoudi et al. – BaNH (Janczyk and Ziuys): DFT calculations  Ba – N triple bond – Small eQq (N) consistent with 4 bonds to N (CH 3 NC eQq (N) = (1) MHz) – Considerable covalent character in Ba – N bond; charge on N = or , calculated eQq (N) = MHz

June 25, th International Symposium on Molecular Spectroscopy Acknowledgements NSF Canisius College Travel Funds