High Resolution Microwave Spectra of High Resolution Microwave Spectra of HeHeNN – and (H – and (H22))NN – Linear Molecule Clusters – Linear Molecule Clusters

Wolfgang Jäger

Department of Chemistry, University of Alberta, Edmonton, AB Canada

Collaborations:Yunjie Xu, UofABob McKellar, NRCPN Roy, Nick Blinov, UofA

(H(H22))NN – Molecule Clusters on this Meeting – Molecule Clusters on this Meeting

• MH15: H2 – C5H5NChakree Tanjaroon

• TE02: (H2)N – N2O, N up to 6Jen Landry

• TE03: (H2)N – OCS, N up to 7Julie Michaud

Wolfgang Jäger

Department of Chemistry, University of Alberta, Edmonton, AB Canada

Collaborations:Yunjie Xu, UofABob McKellar, NRCPN Roy, Nick Blinov, UofA

High Resolution Microwave Spectra of High Resolution Microwave Spectra of HeHeNN – Linear Molecule Clusters – Linear Molecule Clusters

Impetus for HeImpetus for HeNN-Molecule Studies-Molecule Studies• He – OCS, He – HF, etc. studies by Higgins and Klemperer.

• SF6, OCS Helium nanodroplet studies by the Scoles/Lehmann and Toennies/Vilesov groups.

• 50th OSU Symposium, Outstanding Challenges for Molecular Spectroscopy(compiled and distilled by Kevin Lehmann)

V. Towards a true Microscopic Theory of Condensed Matter…e) Improvements in experiments and theory of the size

dependence of molecular properties to better understand the transition from an isolated molecule – small cluster – condensed phase.

A Case in Point: SuperfluidityA Case in Point: Superfluidity

• 4He becomes superfluid below the λ-point (2.17 K).• Frictionless flow, irrotationality, quantized vorticity,

fountain effect …

Andronikashvili experiment

‘Drag’ from normal fluid component causes increase of moment-of-inertia of disk stack.

Confirmation of two–fluid model.

The Microscopic Andronikashvili ExperimentThe Microscopic Andronikashvili Experiment

Grebenev, Toennies, Vilesov, Science 279, 2083 (1998).

Pure 4He droplet

Pure 3He droplet

4He droplet with 20 3He

4He droplet with 40 3He

4He droplet with 60 3He

4He droplet with 1000 3He

Alberta:

Rotational (microwave) spectra of HeN-molecule clusters.Instrument: FTMW Spectrometer, 2.5 - 11 GHz.

Ottawa:

Ro-vibrational (infrared) spectra of HeN-molecule clusters.Instrument: Rapid Scan mid-IR Diode Laser spectrometer.

Instrument and TechniqueInstrument and Technique

Multidimensional Assignment ProcedureMultidimensional Assignment Procedure

• infrared predictions

• sample conditions (pressure, temperature)

• double resonance experiments

• consistency of isotopic data

• spectral fits

HeN-OCS

HeHeNN – Molecule Clusters – Molecule Clusters

Effect of Nozzle Cooling on Cluster FormationEffect of Nozzle Cooling on Cluster FormationHe6-OCS, J=3-2 at 11176.83 MHz, 0.01% OCS in He at 20.4 atm100 averaging cycles

nozzle at room temperatureS/N ~ 2

nozzle at dry ice temperature (-78.5 C)S/N ~ 40

Double Resonance SpectrometerDouble Resonance Spectrometer

Double Resonance SpectrometerDouble Resonance Spectrometer

Double Resonance Experiments on HeDouble Resonance Experiments on He66-OCS-OCS

signal: J-3-2, 11176.83 MHzpump: J=2-1, 7588.75 MHz20 averaging cycles

pump power(continuous)

off

-3 dBm

3 dBm

Double resonance experimentsalso with the ‘decoherence technique’.Brendel, Mäder, OSU Symposium2004, paper TA05.

Vibrational Frequency Shifts of HeVibrational Frequency Shifts of HeNN-OCS Clusters-OCS Clusters

experimental values,Tang et al., Science 297, 2030 (2002).

values from Whaley and co-workers, JCP 115, 10225 (2001).

Paesani, Whaley, JCP 121, 4180 (2004).

Vibrational Frequency Shifts of HeVibrational Frequency Shifts of HeNN-OCS Clusters-OCS Clusters

experimental values,Tang et al., Science 297, 2030 (2002).

values from Whaley and co-workers, JCP 115, 10225 (2001).

Moment-of-Inertia Shifts of IsotopomersMoment-of-Inertia Shifts of Isotopomers

I / amu2

32.2

48.8

35.7

37.4

32.1

Proposed Structure of HeProposed Structure of He88-OCS-OCS

Helium density in HeHelium density in He88-OCS-OCS

P. N. Roy, N. Blinov, private communication.

Spectroscopic Constants of HeSpectroscopic Constants of HeNN-OCS Clusters-OCS ClustersMolecule B / MHz D / MHz

Free OCS 6081.59 1.31x10-5

He-OCS 13208.57

5504.18 4582.80

3661.42

0.950

He2-OCS 5803.39

4546.34 3782.81

3019.28

---

He3-OCS 3104.57 5.11

He4-OCS 2591.95 0.881

He5-OCS 2225.15 0.234

He6-OCS 1910.49 2.60

He7-OCS 1682.98 1.29

He8-OCS 1447.73 2.00

OCS in 4He droplet

(N~3,000)

2194.5(90) 11.4(3)

Rotational Constant vs.Number of He AtomsRotational Constant vs.Number of He Atoms

Quantum Monte Carlo Calculations.Quantum Monte Carlo Calculations.

N. Blinov, X. Song, P. N. Roy, JCP 120, 5916 (2004).S. Moroni et al., Phys. Rev. Lett. 90, 143401 (2003).

Helium Density Profiles in HeHelium Density Profiles in HeNN-OCS-OCS

N. Blinov, X. Song, P. N. Roy, JCP 120, 5916 (2004).

N=5

N=7

N=9

N=6

N=8

N=10

HeN-N2O

HeHeNN – Molecule Clusters – Molecule Clusters

HeHe66-N-N22O in its Principal Inertial Axes SystemO in its Principal Inertial Axes System

J=1-0 Rotational TransitionJ=1-0 Rotational Transition

Inte

nsity

Inte

nsity

Frequency / MHz

He7-14N15NO

He5-14N15NOIn

tens

ity

He12-14N15NO

6792.0 6793.5

5471.5 5473.0

6194.5 6195.5

Rotational Constant vs.Number of He AtomsRotational Constant vs.Number of He Atoms

S. Moroni, N. Blinov, P. N. Roy, J. Chem. Phys 121, 3577 (2004).

Helium droplet valueNauta, Miller, JCP 115, 10254 (2001).

Xu, Jäger, Tang, McKellar, Phys. Rev. Lett. 91, 163401 (2003).

Xu, Jäger, Blinov, Roy, J. Chem. Phys. 124, 081101 (2006).

Helium Density Distributions in HeHelium Density Distributions in HeNN-N-N22OO

N=5

N=9

N=14

N=6

N=10

N=15

Back to HeN-OCS

HeHeNN – Molecule Clusters – Molecule Clusters

Infrared Spectra of HeInfrared Spectra of HeNN-OCS Clusters-OCS Clusters

2062.0 2062.1 2062.2 2062.3

R(0)Transitions

14

1516

1718

20

30

4070 6050

Wavenumber / cm-1

Bob McKellar, paper FD01

0

1e+8

2e+8

3e+8

4e+8

5e+8

6e+8

0

10

20

30

40

50

3000

4000

5000

6000

Am

plitu

de

N, n

umbe

r of h

eliu

m a

tom

s

Frequency / MHz

Nanodroplet value

νJ=1-0 ≈ 2B

J=1-0 MW Transitions of HeJ=1-0 MW Transitions of HeNN-OCS Clusters-OCS Clusters

νJ=1-0 ≈ 2B

400 kHz

0

1e+8

2e+8

3e+8

4e+8

5e+8

6e+8

0

10

20

30

40

50

3000

4000

5000

6000

Am

plitu

de

N, n

umbe

r of h

eliu

m a

tom

s

Frequency / MHz

J=1-0 MW Transitions of HeJ=1-0 MW Transitions of HeNN-OCS Clusters-OCS Clusters

Rudi Lehnig, RD05

7000

0

1e+8

2e+8

3e+8

4e+8

5e+8

6e+8

0

10

20

30

40

50

3000

4000

5000

6000

Am

plitu

de

N, n

umbe

r of h

eliu

m a

tom

s

Frequency / MHz

J=1-0 MW Transitions of HeJ=1-0 MW Transitions of HeNN-OCS Clusters-OCS Clusters

Rudi Lehnig, RD05

7000

Rotational Constant Rotational Constant BB as Function of Cluster Size as Function of Cluster Size

Number of helium atoms, N0 10 20 30 40 50 60 70

Ro

tatio

nal c

ons

tant

, B

" /

MH

z

1500

2000

2500

3000

*nanodroplet B-valueToennies, Vilesov, and co-workersJCP 112, 4485 (2000)

Experiment

S. Paolini et al., JCP 123, 114306 (2005).

Whaley and coworkers, PRL 90, 073401 (2003);JCP 121, 4180 (2004);JCP 123, 114301 (2005).

S. Moroni et al., PRL 90, 143401 (2003).

Rotational Constant Rotational Constant BB as Function of Cluster Size as Function of Cluster Size

Number of helium atoms, N0 10 20 30 40 50 60 70

Ro

tatio

nal c

ons

tant

, B

" /

MH

z

1500

2000

2500

3000

*nanodroplet B-valueToennies, Vilesov, and co-workersJCP 112, 4485 (2000)

Experiment

S. Paolini et al., JCP 123, 114306 (2005).

Whaley and coworkers, PRL 90, 073401 (2003);JCP 121, 4180 (2004);JCP 123, 114301 (2005).

S. Moroni et al., PRL 90, 143401 (2003).

AufbauAufbau of a Helium Solvation Shell Structure of a Helium Solvation Shell Structure

AcknowledgementsAcknowledgements

• Dr. Dominik Bremm• Dr. Rudi Lehnig (RD05)• Dr. Chakree Tanjaroon (MH15)• Jen Landry (TE02)• Julie Michaud (TE03)• Wendy Topic• Qing Wen (TE05)

• NSERC, CFI, ASRIP, University of Alberta, CRC