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

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

2

Fourier Transform Microwave Spectrometer at Wesleyan

3

Laser Ablation

4

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

6

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

7

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.

9

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.

10

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

11

Adventures in Fitting

12

# 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

13

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˚)

14

Comparisons Continued• Hf: [Xe]4f145d26s2

• Th: [Rn]6d27s2

<118˚

107.51(1)˚

15

2nd Highest Occupied MOs

16

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

17

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

18

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

19

LUMO

20

Novick Lab Picture

21