1. High-Resolution Infrared Spectroscopy of the Hydroxymethyl (CH2OH) Radical in Solid Parahydrogen
Morgan E. Balabanoff and David T. Anderson
Department of Chemistry, University of Wyoming
Laramie, WY
This research is sponsored in part by the Chemistry Division of the National Science Foundation (CHE ).
Paper: TF01, 1:30 to 1:45 pm
TF. Mini-Symposium: Spectroscopy of Large Amplitude Motions

2. Hydroxymethyl (CH2OH): one of two isomers
3302 cm-1
methoxy
E. Kamarchik, C. Rodrigo, J.M. Bowman, H. Reisler, and A.I. Krylov, JCP 136, (2012).

3. Hydroxymethyl (CH2OH) spectroscopic parameters
aL. Feng, J. Wei, and H. Reisler, J. Phys. Chem. A 108, 7903 (2004).
bM. E. Jacox, Chem. Phys. 59, 213 (1981).
cR.D. Johnson III and J.W. Hudgens, J. Phys. Chem. 100, (1996).
dJ. Wei, B. Karpichev, and H. Reisler, J. Chem. Phys. 125, (2006).
eM. Ryazanov, C. Rodriogo, and H. Reisler, J. Chem. Phys. 136, (2012).
M.A. Roberts, E.N. Sharp-Williams, D.J. Nesbitt, J. Phys. Chem. A 117, 7042 (2013).
E. Kamarchik, C. Rodrigo, J.M. Bowman, H. Reisler, and A.I. Krylov, JCP 136, (2012).

4. Large amplitude motion (LAM) in CH2OH
barrier
Inversion cm-1
Rotation cm-1
S. Saebø, L. Radom, H.F. Schaefer III, JCP 78, (1983).

5. Quantum solids: Condensed phase LAM
3.79
3.79
de Broglie
de Boer
p-H2 L He Ne Ar Kr Xe pH oD

6. What can IR spectroscopy of CH2OH in pH2 tell us?

7. Large amplitude motion (LAM) in CH2OH
State el vib rot tor ns(weight)
Ka even (3) A
Ka odd (1)
Ka even (1)
Ka odd (3)
M.A. Roberts, E.N. Sharp-Williams, D.J. Nesbitt, J. Phys. Chem. A 117, 7042 (2013).

8. Photolytically generate CH2OH in solid para-H2
Photolysis
CH3OH + hn(193nm) → CH3O + H
→ CH2OH + H
→ CH2O + H2
Fast
CH3O+H2 → CH3OH+H → CH2OH+H2
Medium
H + CH2O → CH2OH + H
→ H2 + CHO
Slow
H + CH3OH → CH2OH + H2
M. Balabanoff and DTA, (in preparation).

9. Assigned CH2OH peaks in solid para-H2
CO stretch

10. Can easily assign CH2OH peaks
Table S2. Peak positions for observed CH2OH transitions.
Mode
Ka'←Ka"
B3LYP
gas
pH2 (Lee)
pH2 (Expt.)
n1 (OH)
1←0
0←0
3823(62)
3674.9
3651.9
n2 (CH2 str)anti
3274(9)
3161.5
3165.3
n3 (CH2 str)sym
3134(18)
3038.5
n4 (CH2 sci)
1482(8)
1457.8
n5 (ip bend)
1356(29)
1332.1
n6 (CO str)
1199(109)
1176(±7)
1179.3
n7 (oop bend)
1052(47)
1046.9
Y-F. Lee, W-T. Chou, B.A. Johnson, D.P. Tabor, E.L. Sibert III, and Y-P. Lee, J. Mol. Spec. 310, (2015).

11. Expected band type of CH2OH peaks in solid para-H2
A-type
n6 (CO stretch) B
A/B-type A
n1 (OH stretch)
M.A. Roberts, E.N. Sharp-Williams, D.J. Nesbitt, J. Phys. Chem. A 117, 7042 (2013).

12. Assigned CH2OH peaks in solid para-H2
A-type
A/B-type

13. Low temperature IR spectroscopy of CH2OH
C-Hsym
a/b-type
C-Hasym
b-type
5.69 cm-1
Ka=0←0
1←0
O-H
a/b-type
A1=6.41, B1=0.96, C1=0.88
(A1-B1)=5.45 cm-1
L. Feng, J. Wei, H. Reisler, J. Phys. Chem. A 108, 7903 (2004).

14. Two different samples with different thermal histories
KAK01145
KAK01135

15. Using isotopic shift to assign OH features
5.66(2)
Calc.* Expt. Ratio
CH2OH
CD2OH
3.57(2)
Ka=1
Ka=0
b-type
a-type
Ka=0
*U. Bozkaya, J.M. Turney, Y. Yamaguchi, H.F. Schaefer III, JCP 136, (2012).

16. Using isotopic shifts to assign OH features
5.66(2)
Calc. Expt. Ratio
CH2OH
CD2OH
CD2OD *
3.57(2)
2.78(1)
*Back of the envelope

17. Now it starts to get crazy…
CH2OH
nCH(sym)
Ka=0←0 - +
gas
28 K
a-type
pgopher -
-3.23 cm-1 + A
12.52 cm-1
pH2
1.8 K
M.A. Roberts, E.N. Sharp-Williams, D.J. Nesbitt, J. Phys. Chem. A 117, 7042 (2013).

18. Summary Partial rotational resolution of CH2OH in solid p-H2
K-structure consistent with isotopic substitution trends, but experimental splittings are larger than predicted!
Still questions remain …
nuclear spin
tunneling splittings
How does the para-hydrogen matrix perturb these LAMs?

19. The people who do the work and funding
Morgan E. Balabanoff
Aaron I. Strom
Wyoming Research Scholar
Fredrick M. Mutunga
This research is sponsored in part by the Chemistry Division of the US National Science Foundation through grant (CHE ). We would also like to acknowledge funds from the UW Research Office for the helium recovery system.

20. H+NO reaction in solid pH2: Experimental protocol
Liquid helium bath cryostat
pre-cooled
pH2 gas
dopant
gas
Deposit crystal at <2.5 K
(rapid vapor deposition) UV
beam
atmosphere
vacuum
pH2
crystal
Photolyze sample
(193 nm, 240 mJ cm-2 pulse-1,
250 Hz)
FTIR
beam
Repeated FTIR scans
(3.6 min acquisition times,
average 16 scans at
0.04 cm-1 resolution)
optical
substrate
radiation
shield
M.E. Fajardo and S. Tam, J. Chem. Phys. 108, (1998).

21. Low temperature IR spectroscopy of CH2OH
mystery peak assigned – CH2OH
8.7 hours
after