1. 1 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Mario E. Fajardo AFRL/MNME, Energetic Materials Branch, Ordnance Division, U.S. Air Force Research Laboratory, 2306 Perimeter Road, Eglin AFB, FL 32542-5910. mario.fajardo@eglin.af.mil Takamasa Momose Division of Chemistry, Graduate School of Science, Kyoto University, Kyoto 605-8502, Japan. *Introduction to MIS in solid parahydrogen (pH 2 ) *IR absorption spectra of CO monomers in solid pH 2 *Crystal Field Theory (CFT) analysis & assignments *Summary Crystal Field Theory Analysis of Rovibrational Spectra of CO Monomers in Solid Parahydrogen

2. 2 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 ortho- and para-hydrogen I.F. Silvera, Rev. Mod. Phys. 52, 393 (1980).T. Oka, Fiz. Nizk. Temp. 22, 134 (1996). Electrostatics: Body fixed  00 = 0.484 ea 0 2 oH 2 (J=1):  = (2/5)  00 = 8.69x10 -41 Cm 2 R nn (pH 2 )  3.8Å E (3.8Å)  10 8 V/m  1 MV/cm

3. 3 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Rapid vapor deposition of solid pH 2 M.E. Fajardo and S. Tam, J. Chem. Phys. 108, 4237 (1998). S. Tam and M.E. Fajardo, Rev. Sci. Instrum. 70, 1926 (1999). S. Tam and M.E. Fajardo, J. Low Temp. Phys. 122, 345 (2001). Deposition conditions: T conv = 15 K  100 ppm oH 2 T conv = 19 K  1000 ppm oH 2  n pH2 /  t = 200 mmol/hr  x/  t = 3.1 mm/hr T sub = 2.4 K  2.9 K T pH2  4.6 K Result: mixed fcc/hcp microstructure in as-deposited samples; can anneal to pure hcp.

4. 4 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 12 C 16 O/pH 2 IR absorptions 13 ppm 12 C 16 O/pH 2, d=2.9 mm, deposited in 60 min @ T=2.4K. Assignments from CFT analysis. " , ||"  polarization vs. hcp c-axis "  "  CO in metastable fcc sites (c) T=2.4K, annealed. (b) T=4.8K. (a) T=2.4K, as deposited.

5. 5 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Devonshire Crystal Field Theory Physical assumptions: (1) Molecular center-of-mass (C.M.) remains fixed at trapping site center. (2) Rigid, undistorted trapping site. Potential for diatomic rotor in O h crystal field: V cry (  ) = -K 4 {P 4 0 (cos  ) + (1/168)P 4 4 (cos  ) cos(4  )} A.F. Devonshire, Proc. Roy. Soc. (London) A153, 601 (1936). 4

6. 6 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 CFT analysis of 12 C 16 O in fcc pH 2 For 12 C 16 O in fcc pH 2 : B eff (pH 2 )  0.79 B e (gas)  E(E g - T 2g )  0.56 B e (gas) green: K 4  +12B e, -19B e red: K 4  +1B e, -1B e  Pure CFT cannot explain both observations simultaneously! Approach: use CFT for M J splittings, treat B eff as an adjustable parameter.  Need alternative explanation for matrix effects on rotational constants. R(1) R(0)

7. 7 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Diatomic rotor in D 3h crystal field six adjustable fitting parameters: vibration:  e rotation: B e, D e,  e crystal field:  2,  3

8. 8 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 CFT analysis of 12 C 16 O in hcp pH 2 constant 12 C 16 O values (cm -1 ) 00 2140.295(2) b [2143.2711] c BeBe 1.577(1) [1.9313] DeDe 0.0271(1)[0.00000612]  e d 0.0129(6)[0.01750] 22 1.026(4) 33 2.523(7) a Values in parentheses are the standard deviation (1  ) of the least squares fitting for the last digit. b Values in square brackets are those in the gas phase. [J.A. Coxon and P.G. Hajigeorgiou, J. Chem. Phys. 121, 2992 (2004).] c The band origin of the gas phase is calculated by  e -2  e x e +(13/4)  e y e. d The ground state rotational constant is B 0 =B e -(1/2)  e and that in the excited state is B v =B e -(3/2)  e. e Fit limited to J=0, 1, & 2 levels. 82% 4400x! ~B e

9. 9 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Fitting results: 12 C 16 O in hcp pH 2 obs (cm -1 )calc (cm -1 )obs.-calc.assignment (J',M')  (J",M") pol. 2134.5512134.552-0.001P(2) hcp (1,1)  (2,2)  2135.204 0.000P(2) hcp (1,0)  (2,1)  2136.7412136.743-0.002P(1) hcp (0,0)  (1,0) // 2137.6072137.6060.001P(1) hcp (0,0)  (1,1)  2140.2682140.2660.002Q(1) hcp (1,1)  (1,1)  2142.953 0.000R(0) hcp (1,1)  (0,0)  2143.818 0.000R(0) hcp (1,0)  (0,0)  2145.2822145.2790.003R(1) hcp (2,1)  (1,0)  2145.9312145.9300.001R(1) hcp (2,2)  (1,1)  2146.142146.142-0.002R(1) hcp (2,1)  (1,1)  2147.12 R(2) hcp ?  2148.6152148.617-0.002S(0) hcp (2,2)  (0,0)  J=3 levels not included

10. 10 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Energy levels: 12 C 16 O in hcp pH 2 8.73 calc ?

11. 11 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 CFT for CO isotopomers in pH 2 Annealed samples at T = 2.4 K. Spectra shifted by subtracting gas-phase R(0) line. isotopomerB eff (pH 2 ) (cm -1 ) B gas (cm -1 ) B eff /B gas 12 C 16 O1.5771.93130.8165 13 C 16 O1.5381.84620.8331 12 C 18 O1.4691.83910.7988 13 C 18 O1.4371.75400.8193 Matrix effect on rotational constant B e depends on CO isotopic composition! (see companion talk RG04).

12. 12 60th International Symposium on Molecular Spectroscopy, Talk RG03, 23 June 2005, Ohio State University, Columbus, OH Approved for Public Release; Distribution Unlimited. AAC/PA 05-03-05-170 Summary * CO monomers exist as hindered rotors in solid pH 2. * Detailed spectroscopic assignments accomplished using Crystal Field Theory for diatomic in D 3h field. * Obtained excellent fits to experimental data. (six parameters vs. ten energy levels)  2,  3 ~ B e B eff (pH 2 )  0.8 B e (gas) D e (pH 2 )  4400 D e (gas) * Matrix effect on rotational constant B e depends on CO isotopomer! (subject of companion talk RG04...)