PURE ROTATIONAL SPECTRA OF THE REACTION PRODUCTS OF LASER ABLATED THORIUM METAL AND OXYGEN MOLECULES ENTRAINED WITHIN SUPERSONIC EXPANSIONS OF NOBLE GASES.

*Brittany E. Long and ǂStephen A. Cooke RC02 June 20, 2013

* ǂ

Thorium• α emitter • t1/2= 1.4 E 10 years

• Solid at 25˚C• MP= 1750 ˚C• BP= 4820 ˚C

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Fourier Transform Microwave Spectrometer at Wesleyan

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Laser Ablation

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THE MOLECULES 5

Calculations• MP2 calculations with aug-cc-pVQZ for main group elements

and a multi-electron, quasi-relativistic, effective core potential, ECP60MWB for thorium• ThS, ThS2, ThOC, ThOS, ThCS,

• For comparison reasons with HfO2, ThO2 was calculated with a B3LYP with aug-cc-pVQZ for O and an ECP60MWB for thorium for ThO2

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ThS• Obtained B value from Professor Michael Heaven.• B= 0.111(2) cm-1 or 3328(60) MHz1,2

• Using ν=2B(J+1)• Transitions should be as follows:

• J 1 0 at 6656(120) MHz• J 2 1 at 13312(240) MHz• J 3 2 at 19968(480) MHz

• No ThS signal found on either the chirp or cavity with OCS or H2S as sulfur source.• Searched 6 GHz with the chirp• Searched 200 MHz twice with the cavity

1. Bartlett, J. H.; Antonov, I. O.; Heaven, M.C. Spectroscopic and Theoretical Investigations of ThS and ThS +. Manuscript in progress.2. Bartlett, J. H.; Heaven, M. C. Ionization Measurement and Spectroscopy of ThS and ThS+. WK15

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Measured J= 1 0 Rotational Transitions for Excited Vibrational States of ThO

Isotope v Frequency/MHz232Th16O 8 19273.9055

9 19194.3480

10 19114.6205

11 19034.7216

12 18957.6471

13 18874.3954

14 18793.9657

15 18713.35108

Previous Dunham Analysis1

Parameter Value

Y01 /MHz 9971.7767(35)

U01 /MHz 149242.742(52)

Y11 /MHz -39.05256(26)

Y21 /MHz -0.039573(33)

ΔO01 -5.970(11)

eQq(17O) v=0 /MHz 2.827(9)

eQq(17O) v=1 /MHz 2.815(9)

CI(17O) v=0 /MHz -0.0108(5)

CI(17O) v=1 /MHz -0.0110(5)

reBO /Å 1.84018613(24)

1. Dewberry, C. T.; Etchison, K. C.; Cooke, S. A. The pure rotational spectrum of actinide-containing compound thorium monoxide. Phys. Chem. Chem. Phys. 2007, 9, 4895-4897.

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ThO Vibrational Temperature

-22000 -20000 -18000 -16000 -14000 -12000 -10000

-4

-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

v=8

v=9

v=10v=11

v=12v=13

v=14

v=15

f(x) = 0.00030518303773321 x + 2.25067481049049R² = 0.920201768053738

Ln (Intensity) vs. Energy/k

-E/k

Ln (i

nten

sity)

Vibrational temperature≈ 3300 K

ThO vibrational frequency is 895.77(2) cm-1 [1]

[1] Edvinsson, G.; Selin, L. E.; Aslund, N. On the band spectrum of ThO. Arkiv Fӧr Fysik. 1965, 30, 283-319.

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4 Thorium Dependent TransitionsPossible Quantum Numbers Frequency/ MHz

303-212 19251.8738

110-101 14628.0470

211-202 16140.3822

312-303 18585.1238

• Laser dependent• Better signal with O2 present• Visible still in Neon • Believed to be ThO2

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Adventures in Fitting

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# Quantum Numbers Frequency /MHz

1 303-212 19251.87381

2 110-101 14628.04700

3 211-202 16140.38217

4 312-303 18585.12377

1, 2 and 3 1, 2 and 4 1, 2, 3 and 4

A 19190.8879(56) 19194.5467(42) 19197.6395(37)

B 5968.89803(95) 5967.37883(61) 5967.68532(58)

C 4562.84090(299) 4566.49974(141) 4567.116531(135)

RMS /MHz 0.0 0.0 2.4

PCC /amu Å2 0.121662 0.174302 0.177479

How to Proceed

• If ThO2, 3 more possible transitions in range of spectrometer

• Currently waiting on 18-26.5 GHz low noise amplifier• Repair of 5 W solid state amplifier

Quantum Numbers Predicted Frequencies/MHz202-111 7734

413-404 22181

111-000 23764

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Comparisons

Bond Length/ Å Bond Angle/ ˚ Ground State Citation

HfO 1.7231481 NA 1Σ 1

HfO2 1.7764(4) 107.51(1) 1A1-C2v sym. 1

ThO 1.84018613(24) NA 1Σ 2

ThO2 1.897 118.33 1A1-C2v sym. This work

1. Lesarri, A.; Suenram, R. D.; Brugh, D. Rotational spectrum of jet-cooled HfO and HfO 2. J. Chem. Phys. 2002, 117, 9651-9662.2. Dewberry, C. T.; Etchison, K. C.; Cooke, S. A. The pure rotational spectrum of actinide-containing compound thorium

monoxide. Phys. Chem. Chem. Phys. 2007, 9, 4895-4897.3. Andrews, A.; Gong, Y.; Liang, B.; Jackson. V. E.; Flamerich, R.; Li, S.; Dixon, D. A. Matrix Infrared Spectra and Theoretical

Studies of Thorium Oxide Species: ThOx and Th2Oy. J. Phys. Chem. A. 2011, 115, 14407-14416. (116.47˚)

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Comparisons Continued• Hf: [Xe]4f145d26s2

• Th: [Rn]6d27s2

<118˚

107.51(1)˚

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2nd Highest Occupied MOs

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Conclusion• Obtained the v=8-15 vibrational levels for ThO• Predicted a vibrational temperature of about 3300 K

• Observed 4 thorium dependent transitions• Most likely ThO2

• Provided interesting comparison between HfO2 and ThO2

• Provide information via microwave spectroscopy to help advance the field of actinide chemistry

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Future Work

• Finish ThO2

• Thorium with 18O2 and 17O2 as well

• Higher ThO vibrational levels of all species• Revisit the Dunham analysis

• ThS and other thorium species• Possible problems • High omega values• Out of range of spectrometers

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Acknowledgements• Novick, Pringle and Cooke Group• Laboratory Funding from the DOE

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LUMO

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Novick Lab Picture

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