Spectroscopy of CuN in the Near Infrared by Intracavity Laser Absorption Spectroscopy Leah C. O'Brien and Kaitlin A. Womack, Department of Chemistry, Southern Illinois University, Edwardsville, IL ; James J. O'Brien,Department of Chemistry and Center for Nanoscience, University of Missouri, St. Louis, MO 63121

Previous Work on CuN  No previous experimental work  Several papers on ground state bond length and symmetry, 3 Σ -  Ground and excited potential energy curves calculated by A. Daoudi, A. Touimi Benjelloun, J.P. Flament, and G. Berthier, J. Mol. Spectrosc. 194 (1999) 8-16 X 3 Σ - A 3 Π at 1.5 eV

MO Energy Level Diagram for CuN Fenske-Hall Calculation

Intracavity Laser Absorption Spectroscopy  Absorption spectra recorded using intracavity laser spectrometer at the University of Missouri – St. Louis  Configured with a copper hollow cathode plasma discharge operating at high current, 1.5 A, from DCG power supply  Pressures of 1.5 Torr of oxygen was employed  Generation times (t g ) up to 200 µs were used, the copper hollow cathode was 50 mm long, the overall laser cavity length was 2.30 m  Spectra are recorded as a series of overlapping spectral segments, each segment being ̴ 6 cm −1 wide

Copper Hollow Cathode Discharge

Results  New spectrum with red-degraded band heads at , , , and cm cm -1 band  Shows a single P- and R-branch  Identified line positions in each branch  Used Excel to graph line positions and the difference between peaks  Possibly (0,0) band of A 3 Π 0 – X 3 Σ - 0 ?

Portion of the CuN spectrum associated with the cm -1 band

Unusual line spacing in both branches

Useful to get J assignments! 5. H.D. Babcock and L. Herzberg, Ap. J. 108 (1948)  One and only one assignment gives unperturbed ground state! Cm -1 J

Partial line list for cm -1 band

Ground state Δ 2 F values for cm -1 band  Δ 2 F = 4B (J + 0.5) x-intercept should go through J = -0.5 y-intercept should be 2B  Confirms that J is integer  Not CuO! (also checked Δ 2 F values for X 2 Π 3/2, X 2 Π 3/2 )  E J = B J(J+1) – D J 2 (J+1) 2  Fit to get molecular constants B0B0 D 0 x 10 6 r 0 (Å) Ground state (35)0.687(14)1.823 Ab initior e =1.811

X 3Σ-1X 3Σ-0X 3Σ-1X 3Σ-0 A 3Π0A 3Π0 40 cm -1

cm -1 band  1 R- and P-branch Branches have regular spacing  Fit as Ω=0 – Ω=0 transition  Possibly (1,1) bandhead? TvTv BvBv D v x 10 6 Excited statex (63)0.896(68) Lower statex (63)0.899(57)

Spectrum of CuN? Pros  “Ok” match with predicted ground state bond length  Not CuO, not O 3  A 3 Π 0 - X 3 Σ - 0 should be a single P- and R-branch  Other nearby bandheads could be related to A 3 Π 0 - X 3 Σ - 1 transition Work in progress!!  b 1 Δ state predicted near A 3 Π – could be perturbing state  Isoelectronic NiO has X 3 Σ - with λ ss = 25 cm -1 Cons  Only “Ok” match with ground state bond length  Calculation predicts A 3 Π – X 3 Σ - should be blue- degraded R e ” = a 0 = Å R e ’ = a 0 = Å However, calculation did not include spin-orbit effects Perturbing states near excited state  No evidence of 63 Cu/ 65 Cu isotope structure

Summary  Four newly-observed bandheads are tentatively assigned to CuN  cm -1 band contained single P- and R-branch Perturbations in excited state Ground state Δ 2 F values fitted Molecular constants for ground state obtained  cm -1 band contained single P- and R-branch No perturbations in excited state, molecular constants obtained for both states (1,1) band?  Work in progress on other bandheads

Acknowledgements  National Science Foundation  Kaitlin Womack, undergraduate student at SIU Edwardsville  Thank you for your attention !

B eff (J)= E J /[J(J+1)]