Infrared Intensity and Spectra of Infrared Intensity and Spectra of NN22-H-H22O, OO, O22-H-H22O and Ar-HO and Ar-H22OO

in He Dropletsin He Droplets

Susumu Kumaa), Mikhail N. Slipchenkob), Kirill E. Kuyanovb), Takamasa Momosec), and Andrey F. Vilesovb)

a) Kyoto University

b) University of Southern California

c) The University of British Columbia

SUN

EARTH

Infrared Intensity ofInfrared Intensity ofX-HX-H22O in AtmosphereO in Atmosphere

HH22OO X-HX-H22OO

IR

IR

H2O

X-H2O

Key of earth’s radiation balance

Large “infrared intensity” A(H2O)

X = N2, O2, Ar, etc.

Infrared intensity A(X-H2O)

Theory: A(N2–H2O) ~ 2 A(H2O)Experiment: not determined

?

Infrared Intensity of ComplexInfrared Intensity of ComplexDifficult to determine experimentally.

IR IR

AbsorbanceAbundance of

complex ?

Helium DropletsHelium DropletsAbundance of complexes

can be precisely determined.

Spectroscopy Using He DropletsSpectroscopy Using He Droplets

gas cellcryogenic

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 spectraExtremely small perturbation to ro-vibrational spectra

He droplet production

T = 16 KP = 20 bar

nozzle

He droplets<NHe> = 3500

T = 0.4 K

Abundance of Complexes in He DropletsAbundance of Complexes in He Droplets

gas cell moleculeHe droplet

pressure in gas cell

N = 1 N = 2 N = 3

Poisson distribution

NN = 0 = 0

PN

Pressure p

NN = 1 = 1

NN = 2 = 2

NN = 3 = 3

NN = 4 = 4

Abundance ratio

=IN=1

IN=2 PN=1

PN=2 AN=1

AN=2

Infrared intensity ratio

NN = 1 = 1 NN = 2 = 2

Absorbance ratio

ex.)

precisely determined

Objective of This StudyObjective of This StudyExperimental determination of the infrared intensity of X-H2O in the H2O ν3 mode using helium droplets

(X = N2, O2 & Ar)

ExperimentalExperimental

Infrared spectra

Abundance ratio

Infrared intensity of X-H2OPressure p(X)

Abu

ndan

ce

H2O

X-H2OX2-H2O

Wavenumber / cm-1

NN22-H-H22OO

Wavenumber / cm-1

(H2O)2(H2O)2

000101 101000

202101p(H2O) = 3×10-4Pa

p(N2) = 9×10-4Pa

Wavenumber / cm-1

Subtracted

H2O only

H2O & N2

NN22-(H-(H22O)O)22

H2O

N2-H2O

(N2)2-H2O

NN22-H-H22OO(N(N22))22-H-H22OO

3020100

p(N2) / 10-3 Pa

3746.2 cm-1

3749.8 cm-1

3778.0 cm-1

(H2O)2 RA07 by KuyanovH2O

OO22-H-H22O O & Ar-H& Ar-H22OO

p(H2O) = 6×10-4Pa

p(O2) = 9×10-4Pa

p(Ar) = 12.5×10-4Pa

H2O only

Wavenumber / cm-1

Wavenumber / cm-1

Wavenumber / cm-1

H2O & O2

H2O & Ar

(H2O)2 (H2O)2

000101101000

202101

p(O2) / 10-3 Pa

H2O

O2-H2O

OO22-H-H22OO

Ar-HAr-H22OO

p(Ar) / 10-3 Pa

H2O

Ar-H2O

Infrared Intensity Infrared Intensity AA of X-H of X-H22OO

543210

p(N2) / 10-4 Pa

Abu

ndan

ce H2O

N2-H2O

&

XThis work Theory*

N2 1.3 ± 0.3

1.0 ± 0.3

1.1 ± 0.3

2.0

1.2

1.4

O2

ArEnhanced infrared intensities by up to 30 %

*Kjaergaard et al., J. Phys. Chem. A 107, 10680 (2003)

Changes of the dipole moment of H2Odue to charge redistribution

H2ON2-H2O

Wavenumber / cm-1

Abs

orba

nce

Spectral Structure of Spectral Structure of NN22-H-H22O, OO, O22-H-H22O, and Ar-HO, and Ar-H22OO

N2–H2O

O2–H2O

Ar–H2O

Wavenumber / cm-1

H2OX-H2O

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 H2O

free rotation

free rotation

no rotation

SummarySummary

AcknowledgementsAcknowledgementsNSF, NSERC & JSPS

We applied helium droplets successfully to the infrared intensity determination of N2-H2O, O2-H2O, and Ar-H2O complexes.

Small enhancement of infrared intensity of H2O

N2-H2O 1.3 ± 0.3

O2-H2O 1.0 ± 0.2

Ar-H2O 1.1 ± 0.2

Free rotation of H2O: O2-H2O and Ar-H2ONo rotation: N2-H2O

Rotational energy levels of H2O

Energy Diagram of Ar-HEnergy Diagram of Ar-H22OO

> T = 0.4 K

K. MatsumuraG. A. BlakeD. J. NesbittR. J. Saykally

H2OAr-H2O

Wavenumber / cm-1

m–splitting

|mj| = 0, 1, 2...

ΣΠΔ

para ortho

101000000101 202101

H2ON2-H2O

N2–H2O

a-type band

b-type band

Wavenumber / cm-1

a-axis

b-axis

transition moment of 3