1. Infrared Intensity and Spectra of N 2 -H 2 O, O 2 -H 2 O and Ar-H 2 O in He Droplets Susumu Kuma a), Mikhail N. Slipchenko b), Kirill E. Kuyanov b), Takamasa Momose c), and Andrey F. Vilesov b) a) Kyoto University b) University of Southern California c) The University of British Columbia

2. SUN EARTH Infrared Intensity of X-H 2 O in Atmosphere H2OH2OH2OH2O X-H 2 O IR H2OH2O X-H 2 O Key of earth’s radiation balance Large “infrared intensity” A(H 2 O) X = N 2, O 2, Ar, etc. Infrared intensity A(X-H 2 O) Theory: A(N 2 –H 2 O) ~ 2 A(H 2 O) Experiment: not determined ?

3. Infrared Intensity of Complex Difficult to determine experimentally. IR Absorbance Abundance of complex ? Helium Droplets Abundance of complexes can be precisely determined.

4. Spectroscopy Using He Droplets gas cell cryogenic nozzle quadrupole mass spectrometer laser Pickup by collision Detection absorption and relaxation evaporation of He depletion of mass signal reduction of cross-section Extremely small perturbation to ro-vibrational spectra He droplet production T = 16 K P = 20 bar nozzle He droplets = 3500 T = 0.4 K

5. Abundance of Complexes in He Droplets gas cell molecule He droplet pressure in gas cell N = 1N = 2N = 3 Poisson distribution N = 0 PNPN Pressure p N = 1 N = 2 N = 3 N = 4 Abundance ratio  = I N=1 I N=2 P N=1 P N=2 A N=1 A N=2 Infrared intensity ratio N = 1 N = 2 Absorbance ratio ex.) precisely determined

6. Objective of This Study Experimental determination of the infrared intensity of X-H 2 O in the H 2 O ν 3 mode using helium droplets (X = N 2, O 2 & Ar) Experimental Infrared spectra Abundance ratio Infrared intensity of X-H 2 O Pressure p(X) Abundance H2OH2O X-H 2 O X 2 -H 2 O

7. Wavenumber / cm -1 N 2 -H 2 O Wavenumber / cm -1 (H 2 O) 2 0 00  1 01 1 01  0 00 2 02  1 01 p(H 2 O) = 3×10 -4 Pa p(N 2 ) = 9×10 -4 Pa Wavenumber / cm -1 Subtracted H 2 O only H 2 O & N 2 N 2 -(H 2 O) 2 H2OH2O N 2 -H 2 O (N 2 ) 2 -H 2 O N 2 -H 2 O (N 2 ) 2 -H 2 O p(N 2 ) / 10 -3 Pa 3746.2 cm -1 3749.8 cm -1 3778.0 cm -1 (H 2 O) 2 RA07 by KuyanovH2OH2O

8. O 2 -H 2 O & Ar-H 2 O p(H 2 O) = 6×10 -4 Pa p(O 2 ) = 9×10 -4 Pa p(Ar) = 12.5×10 -4 Pa H 2 O only Wavenumber / cm -1 H 2 O & O 2 H 2 O & Ar (H 2 O) 2 0 00  1 01 1 01  0 00 2 02  1 01 p(O 2 ) / 10 -3 Pa H2OH2O O 2 -H 2 O Ar-H 2 O p(Ar) / 10 -3 Pa H2OH2O Ar-H 2 O

9. Infrared Intensity A of X-H 2 O p(N 2 ) / 10 -4 Pa Abundance H2OH2O N 2 -H 2 O & X This workTheory* N2N2 1.3 ± 0.3 1.0 ± 0.3 1.1 ± 0.3 2.0 1.2 1.4 O 2 Ar Enhanced infrared intensities by up to 30 % *Kjaergaard et al., J. Phys. Chem. A 107, 10680 (2003) Changes of the dipole moment of H 2 O due to charge redistribution H2OH2O N 2 -H 2 O Wavenumber / cm -1 Absorbance

10. Spectral Structure of N 2 -H 2 O, O 2 -H 2 O, and Ar-H 2 O

11. N 2 –H 2 O O 2 –H 2 O Ar–H 2 O Wavenumber / cm -1 H2OH2O X-H 2 O K. Matsumura et al. G. A. Blake et al. D. J. Nesbitt et al. R. J. Saykally et al. F. J. Lovas et al. Internal rotation of H 2 O free rotation no rotation

12. Summary Acknowledgements NSF, NSERC & JSPS We applied helium droplets successfully to the infrared intensity determination of N 2 -H 2 O, O 2 -H 2 O, and Ar-H 2 O complexes. Small enhancement of infrared intensity of H 2 O N 2 -H 2 O1.3 ± 0.3 O 2 -H 2 O1.0 ± 0.2 Ar-H 2 O1.1 ± 0.2 Free rotation of H 2 O: O 2 -H 2 O and Ar-H 2 O No rotation: N 2 -H 2 O

14. Rotational energy levels of H 2 O Energy Diagram of Ar-H 2 O > T = 0.4 K K. Matsumura G. A. Blake D. J. Nesbitt R. J. Saykally H2OH2O Ar-H 2 O Wavenumber / cm -1 m–splitting |m j | = 0, 1, 2...  Π  Δ  para ortho 1 01  0 00 0 00  1 01 2 02  1 01

15. H2OH2O N 2 -H 2 O N 2 –H 2 O a-type band b-type band Wavenumber / cm -1 a-axis b-axis transition moment of 3