June 25, 2015 70 th International Symposium on Molecular Spectroscopy Hyperfine Resolved Pure...

June 25, 201570th International Symposium on Molecular Spectroscopy

Hyperfine Resolved Pure Rotational Spectroscopy of ScN, YN, and BaNH (X 1S+):

Insight into Metal – Nitrogen Bonding

Lindsay N. Zack, Matthew P. Bucchino, Justin Young, Marshall Binns, Phillip M. Sheridan, and

Lucy M. ZiurysDepartment of Chemistry and Biochemistry, University of

ArizonaDepartment of Chemistry and Biochemistry, Canisius College


Previous Work• ScN

– Experimental:• Ram and Bernath: FT emission spectroscopy A1S+–X1S+

(Dv = 0); Equilibrium rotational parameters• Nakhate and Mukund: Jet-cooled LIF; B1, C1, D1 and

a3S+ states (Dv ≠ 0); rotational constants and fundamental vibrational frequencies

– Computational: 1S+ ground state• Daoudi and coworkers: CIPSI, Sc–N double bond

diradical• Kunze & Harrison: MC-SCF, highly ionic Sc–N triple

bond


Previous Work

• YN– Experimental:

• Ram & Bernath: FT emission spectroscopy A1S+–X1S+ (Dv = 0); Equilibrium rotational parameters

• Jakubek et al.: Jet-cooled LIF; B1, C1, D1 and a3S+ states (Dv ≠ 0); rotational constants and fundamental vibrational frequencies

– Computational: 1S+ ground state• Shim & Gingerich: CASSCF, Y–N double bond


Previous Work

• BaNH– Experimental:

• Janczyk and Ziurys: MM-wave: 138BaNH, 137BaNH,

138BaND, and 138BaND; r0, rs, and rm(1);

– Computational: 1S+ ground state • Linear; DFT: Ba – N triple bond, not purely ionic

• No experimental M or N hyperfine parameters for ScN, YN and BaNH


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


Discharge Assisted Laser Ablation (DALAS)• Ablation laser: Nd:YAG

(532nm, 200 mJ per pulse; 10 Hz rep rate; 990 ms delay)

• DC discharge 1250 V (Y, Sc) or 1000 V (Ba)

• Metal vapor reacted with 0.2% 14NH3 or 15NH3 in Ar

Ba Rod

31471.8 31472.1 31472.431465.5 31465.8 31466.131463.1 31463.4 31463.7

Frequency (MHz)

33138.8 33139.1 33139.4 33147.5 33147.8 33148.133141.2 33141.5 33141.8

F1 = 2.5 → 3.5 F1 = 4.5 → 3.5 F1 = 3.5 → 3.5

F = 2 → 3 F = 5 → 4

F = 4 → 3 F = 4 → 4

ScN (X1Σ+): J = 1 → 0

F = 4 → 3 F = 4 → 4F = 3 → 3F = 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

Sc14N

Sc15N

F = 3 → 3 F = 3 → 4

F1 = J + ISc

F = F1 + IN

24117.3 24117.4 24117.5 24117.6 24117.7 24117.8

Frequency (MHz)

YN (X1Σ+): J = 1 → 0

25582.6 25582.8 25583

F1 = 1 → 1 F = 1.5 → 0.5 F = 1.5 → 1.5

F1 = 1 → 1 F = 0.5 → 0.5 F = 0.5 → 1.5

F1 = 2 → 1F = 2.5 → 1.5

F1 = 2 → 1 F = 1.5 → 0.5 F = 1.5 → 1.5

F1 = 0 → 1 F = 0.5 → 0.5 F = 0.5 → 1.5

F1 = 1.5 → 0.5 F = 2 → 1

F1 = 1.5 → 0.5 F = 1 → 0 F = 1 → 1

F1 = 0.5 → 0.5 F = 1 → 0 F = 1 → 1

F1 = 0.5 → 0.5 F = 0 → 1

Y14N

Y15N

F1 = J + IN

F = F1 + IY

Also J = 2 → 1

15968.90 15968.95 15969.00 15969.05 15969.10 15969.15

138Ba14NH (X1Σ+): J = 1 → 0

Frequency (MHz)

F = 1 → 1

F = 2 → 1

F = 0 → 1

~

F = J + IN

IN = 1


DFT Calculations• Used to estimate hyperfine parameters (in MHz)

• Order of magnitude agreement between basis sets

Molecule Basis Set eQq (M) CI (M) eQq (N) CI (N)Sc14N aug-cc-pVTZ 45.540 0.05037 -0.4385 0.01096

aug-cc-pVTZ (N)/LANL2DZ (M) 14.671 0.05559 -0.5363 0.01099 SDD 13.508 0.05856 -0.1540 0.009174 exp 33.818 0.05553 -0.127 0.0073

Sc15N aug-cc-pVTZ 45.540 0.04781 -0.01459 aug-cc-pVTZ (N)/LANL2DZ (M) 14.671 0.05277 -0.01464 SDD 13.508 0.05559 -0.01222 exp 33.818 0.05275 -0.0085

Y14N aug-cc-pVTZ (N)/LANL2DZ (M) 0.001785 -1.076 0.008638 SDD -0.001749 -0.9251 0.007333 exp -0.0076 -0.307 0.0081

Y15N aug-cc-pVTZ (N)/LANL2DZ (M) -0.001682 -0.011142 SDD -0.001649 -0.009695 exp -0.0069 -0.0104

BaNH SDD 1.38 0.001840 exp 0.039


Sc14N Sc14N Sc15N Y14N Y14N Y15N BaNH BaNHB 16571.5278(10) 16571.42(23) 15733.6921(14) 12791.4396(32) 12791.237(17) 12058.8364(27) 7984.5273(18) 7984.5488(29)D 0.031502(39) 0.0217(13) 0.021262(20) 0.0186(13) 0.005711(11) 0.0057642(19)H -5.4(1.9) x 10-8 L 1.98(94) x 10-11 eQq(M)

33.818(19) 33.811(30)

CI(M) 0.05553(63) 0.05275(77) -7.6(5.7) x 10-3 -6.9(3.8) x 10-3 eQq(N) -0.127(19) -0.307(10) 0.039(11) CI(N) 7.3(3.0) x 10-3 -8.5 (6.1) x 10-3 8.1 (2.3) x 10-3 -10.4 (3.1) x 10-3 rms 0.001 0.001 < 0.000 0.001 0.026 0.029

Constants (MHz)

• Previous work• BaNH: Combined fit with mm-wave data• Experimental signs of eQq and CI match DFT and

experimental intensities for BaNH


Nuclear Spin – Rotation: Sc and YCI scales as gI × B (pairs of isotopologues)

Molecule (Nucleus)

ScN (Sc) 1.052 1.053

ScN (N) -0.86 -0.75

YN (Y) 1.1 1.1

YN (N) -0.78 -0.76


• ScF and ScO: – s 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 QuadrupoleMolecule eQq (MHz)

ScF 74.086(15)ScO 72.240(15)ScN 33.818(19)

s HOMO


Nitrogen Electric QuadrupoleMolecule eQq (MHz)

ScN -0.127(19)TiN -1.515(19)CrN -2.080(27)YN -0.3065(50)

MoN -2.31(17)BaNH 0.039(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): nhyb= 3.01, npx= npy=1.27; eQq(N) = -2.63 MHz– ScN (Daoudi et al.): nhyb= 2.63, npx= npy=1.29; eQq(N) = -0.260 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)


Nitrogen Electric QuadrupoleMolecule eQq (MHz)

ScN -0.127(19)TiN -1.515(19)CrN -2.080(27)YN -0.3065(50)

MoN -2.31(17)BaNH 0.039(11)

– YN (Shim and Gingerich): AO populations eQq(N) = -1.51 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 (CH3NC eQq (N) = 0.4885(1) MHz)– Considerable covalent character in Ba – N bond; charge on N = -0.15 or -0.953,

calculated eQq (N) = 0.039 MHz


Acknowledgements

• NSF• Canisius College Travel Funds

June 25, 2015 70 th International Symposium on Molecular Spectroscopy Hyperfine Resolved Pure...

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