1. MICROWAVE OBSERVATION OF THE VAN DER WAALS COMPLES O2-CO
F. E. Marshall, Thomas D. Persinger, David Joseph Gillcrist, Nicole Moon, Steve Ndengue, Richard Dawes, and G. S. Grubbs II
71st International Symposium on Molecular Spectroscopy
June 20-24, 2016, Urbana-Champaign, IL, USA; WG14

2. O2 Complexes Are Rare
Making up 21% of our atmosphere, O2 complex studies are quite rare- Only 5 different complexes mentioned on Stew Novick’s Bibliography1: Ar-O2, DCl-O2, SO2-O2, N2O-O2, and O2-O2
Unfinished work of O2-OCS by Brian Howard2 and
H2O-O2 by Endo and coworkers3
Why???
WA10: INFRARED SPECTRUM OF CO-O2, A 'NEW' WEAKLY-BOUND COMPLEX; Bob McKellar, A. J. Barclay, K. H. Michaelian, Nasser Moazzen-Ahmadi
Stew Novick. BIBLIOGRAPHY OF ROTATIONAL SPECTRA OF WEAKLY BOUND COMPLEXES.
Brian Howard, Private Communication.
Y. Kasai, E. Dupuy, R. Saito, K. Hashimoto, A. Sabu, S. Kondo, Y. Sumiyoshi, and Y. Endo, Atmos. Chem. Phys., 11 (2011),

3. Chirp Results 1% CO, 5% O2 in He 1 atm backing pressure 20k FIDs
500 MHz Chirp ( GHz)
50k FIDs
500 MHz Chirp ( GHz)

4. Cavity Results 1% CO, 5% O2 in He (different gas mix)
2 atm backing pressure
No Helmholtz Coils
No splitting!!!
1500 nozzle pulses
74:1 S:N

5. O2-OCS Comparison
Brian Howard, Private Communication and B. J. Howard, 57th ISMS TI01
Splitting?! Needed Helmholtz coils to null field! Complicated Hamiltonian due to O2 dynamics!

6. O2-OCS Hamiltonian
JKa Kc - JKa Kc
Observed/MHz
Obs-calc/MHz
0.366
-0.100
-0.149
0.303
-0.020
-0.181
0.235
0.104
0.610
-0.311
0.308
0.159
0.175
-0.187
0.080
0.073
0.213
-0.106
-0.432
-0.269
JKa Kc - JKa Kc
Observed/MHz
Obs-calc/MHz
0.268
-0.251
202101
-0.112
303202
0.114
0.346
-0.353
-0.593
-0.159
0.568
0.021
-0.493
-0.310
0.333
0.064
-0.313
-0.307
0.583
0.471
-0.255
-0.340
A /MHz
(24)
B /MHz
(1)
C /MHz
(1)
DJ /MHz
(2)
DJK /MHz
(2)
DK /MHz
(2)
d1 /MHz
(3)  90 
 /GHz
83.3
 /MHza
18.3
Cannot fit these using standard semirigid Hamiltonian;
Tried to recreate Howard’s assignments in Pickett’s code with no luck

7. O2-H2O Comparison
Y. Kasai, E. Dupuy, R. Saito, K. Hashimoto, A. Sabu, S. Kondo, Y. Sumiyoshi, and Y. Endo, Atmos. Chem. Phys., 11 (2011),
No Paramagnetic Splitting?

8. O2-H2O Hamiltonian
Y. Kasai, E. Dupuy, R. Saito, K. Hashimoto, A. Sabu, S. Kondo, Y. Sumiyoshi, and Y. Endo, Atmos. Chem. Phys., 11 (2011),
Using SPCAT, we can predict these transitions with obs-calc for O2-H2O

9. O2-CO?
Some preliminary calculations indicated the following structure:
Parameter
Value (MHz) A
28626 B
2902.4 C
2635.2
Calculations ran at uMP2/aug-cc-pVQZ level
Transitions needed each component of the O2-CO in He mixture. The transition did not appear with previously tested O2-OCS molecule. Furthermore, He-CO was not visible when this mix was made.

10. O2-CO Theory (Dawes Group)
GLOBAL MINIMUM, R=3.46Å
LOCAL MINIMUM, R=3.82Å

11. O2-CO Theory (Dawes Group)
GLOBAL MINIMUM, R=3.46Å, cm-1
LOCAL MINIMUM, R=3.82Å, cm-1
He-CO is predicted to be -22.9cm-1,a
a. C. E. Chuaqui, R. J. Le Roy, A. R. W. McKeller, JCP 101 (1994) 39.

12. Interesting Developments
Brian Howard’s Private Communication says that the spin is linked to the Ka term in O2-OCS. These levels will not be split if Ka=0.
Prediction with λ=59.5 GHz as in free O2 gives a close Ka=0 transition to our line with reasonable intensity.
303 – 202?

13. Acknowledgements GSGII: Missouri S&T Startup; UM Research Board Grant
Dawes: NSF  CHE