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 62026-1652;

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, 3Σ-

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 3Σ-

• A 3Π 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 (tg) 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

ResultsNew spectrum with red-degraded band heads at

13004.6, 12962.9, 12957.4, and 12947.9 cm-1

13004.6 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 3Π0 – X 3Σ-0?

Portion of the CuN spectrum associated with the 13004.6 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) 167-190.

One and only one assignment gives unperturbed ground state!

Cm

-1

J

Partial line list for 13004.6 cm-1 band

Ground state Δ2F values for 13004.6 cm-1 band

Δ2F = 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 Δ2F values for X 2Π3/2 , X 2Π3/2)

EJ = B J(J+1) – D J2(J+1)2

Fit to get molecular constantsB0 D0 x 106 r0 (Å)

Ground state

0.442845(35) 0.687(14) 1.823

Ab initio re=1.811

X 3Σ-1 X

3Σ-0

A 3Π0

40 cm-1

12957.4 cm-1 band

1 R- and P-branch• Branches have regular spacing

Fit as Ω=0 – Ω=0 transitionPossibly (1,1) bandhead?

Tv Bv Dv x 106

Excited state x + 12954.333

0.402133(63) 0.896(68)

Lower state x 0.439722(63) 0.899(57)

Wavenumber (cm-1)

12948 12950 12952 12954 12956 12958

Tra

nsm

itta

nce

(%)

75

80

85

90

95

100

Angstrom (Å)7715771777197721

97

100

I2

CuN

RR36 34 32

26 24 14162022 18

Spectrum of CuN?

Pros

“Ok” match with predicted ground state bond length

Not CuO, not O3

A 3Π0 - X 3Σ-0 should be a

single P- and R-branch

Other nearby bandheads could be related to A3Π0 - X 3Σ-

1 transition

• Work in progress!!

b 1Δ state predicted near A 3Π – could be perturbing state

Isoelectronic NiO has X 3Σ-

with λss = 25 cm-1

Cons

Only “Ok” match with ground state bond length

Calculation predicts A 3Π – X 3Σ- should be blue-degraded

• Re” = 3.426 a0 = 1.812 Å

• Re’ = 3.372 a0 = 1.784 Å

• However, calculation did not include spin-orbit effects

• Perturbing states near excited state

No evidence of 63Cu/65Cu isotope structure

SummaryFour newly-observed bandheads are tentatively

assigned to CuN

13004.6 cm-1 band contained single P- and R-branch

• Perturbations in excited state

• Ground state Δ2F values fitted

• Molecular constants for ground state obtained

12957.4 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!

Beff (J)= EJ/[J(J+1)]