Submillimeter-wave and far-infrared spectroscopy of high-J transitions of ammonia

S. Yu, J.C. Pearson, B.J. Drouin and K. Sung

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109

O. Pirali, M. Vervloet and M.-A. Martin

Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif-sur-Yvette, FranceC.P. Endres

I. Physikalisches Institut, Universität zu Köln, 50937 Köln, GermanyT. Shiraishi, K. Kobayashi and F. Matsushima

Department of Physics, University of Toyama, Gofuku, Toyama 930-8555, Japan

Copyright 2010 California Institute of Technology. Government sponsorship acknowledged.

Hot ammonia in space

Shanshan Yu Hot ammonia

•Observed at J=18 (E = 3130 K) toward Sgr B2 (Wilson 2006)

•Expected to exist to larger QN’s in many exoplanets and brown dwarfs

•Numerous studies on GS and 2

−Summarized in Chen 2006; Reduced RMS = 1 (J≤22)

•Two global analyses on 22/4 (5-8 µm)

−Sasada 1992, Cottaz 2000; Reduced RMS = 10 (J ≤ 15)

•One analysis on 24/1/3 (3 µm)

−Kleiner 1999; Reduced RMS = 170 (J ≤ 10)

NH3 spectroscopy in lab

Project goals

– Measure every ammonia terahertz transition the Herschel/HIFI instrument might see (1910–1410 GHz; 1250–480 GHz)

– Measure the 4–22 transitions and figure out why the Hamiltonian doesn’t fit the problematic 4 and 22 states

– Measure the ground state, 2, 22, 4 transitions up to extremely high J, with the goal to provide a list of experimental rovibrational energy levels

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Summary of NH3 experiments in this work

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•177 terahertz GS and 2=1 inversion transitions in 0.3-4.7 THz

•About 2000 far-IR transitions assigned to GS and 2=1

•About 1800 far-IR transitions assigned to 22/4

Extrapolate to zero pressure frequency

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2(a)–2(s) KJ(J, K)= QQ(8, 4)

Shanshan Yu

Global analysis of GS and 2

Hot ammonia

Hamiltonian for GS and 2

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• Standard rotation-inversion Hamiltonian, K=3 and 6 sufficient to fit GS and 2 with J up to 35

− 4394 transitions and 475 comb. diffs. fitted to 212 parameters− A reduced RMS of 0.9 for all data

Summary of rms fit errors (in cm-1)

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2(a)–2(s) KJ(J, K)= QQ (23, 20) from JPL

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FWHM = 3.4 MHz

FT emission spectrum from Synchrotron SOLEIL

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521.5 521.6 521.7 521.8

QP

(23,

10),

2(a)(

s)

QP

(21,

15),

2(s)(

a)

QR

(26,

25),

(s)

(a)

QR

(27,

20),

(a)

(s)

QR

(28,

12),

(a)

(s)

QR

(28,

12),

(s)

(a)

Wavenumber (cm-1)

QR

(28,

24),

2(s) 2(a

)

FWHM = ~0.004 cm-1

FT absorption spectrum from Synchrotron SOLEIL

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NR(3, 3), 2(a)-2(a)

pp (7, 4), 22(a) -a), FWHM = ~0.001 cm-1

QR(3, 0), 2(a)-2(s)

(J’,K’)=(4, 0), 2(a)

Intensity studies:•Fabian, 1995•Fabian, 1999•Brown, 1994•Nemtchinov, 2004

Intensity problem with K=3 lines

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0(a)-0(a)

(11,1)-(10,2)

QR(12,10), 2(s)-2(a)

QR(10,5), 4(a), l=-1 to 4(s), l=-1

K=3 Herman-Wallis terms not included in intensity calculations

0(s)-0(s)

Status on 22/4

• 6174 transitions constructed (1864 from this work), J<16• RMS = 4

Shanshan Yu Hot ammonia

1;2 lK

1 lK

0;3 lK

1;4 lK

2 lK

2;1 lK

2;4 lK2;8 lK

0

500

1000

1500

2000

>>

5

4

l = -1 or 1

4

2

2

gs

E = 35.69

sa

a

s

sa

a

s

E = 0.79

E = 284.70E = 1.10

cm-1

l = 0s

10

32

7 l=-16 l=1

9 l=-18 l=1

3)( lK

6)( lK

0)( lK

Pearson et al., OSU, RC02 (Thursday, 8:46 am)

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Acknowledgements

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• Dr. L. Brown

• Dr. I. Kleiner

• D. Balcon and the AILES beamline staff

• NASA Astrophysics Research and Analysis Program (APRA)

Herschel-HIFI (Heterodyne Instrument for the Far-IR) ESA and NASA joint mission Launch: 2009 (3 years lifetime) Telescope: 3.5 meter diameter, <100 K temperature The only space facility dedicated to the terahertz part of the spectrum Spectral coverage: 151–212 μm (1910–1410 GHz); 240–625 μm (1250–480 GHz) Objectives: life cycle of gas and dust

New terahertz telescopes (I)

SOFIA (Stratospheric Observatory For Infrared Astronomy ) NASA and DLR, German Aerospace Center joint mission

Operation: 2010 (20 years lifetime)

The largest airborne observatory in the world

Telescope: 2.5 meter diameter, 240 K temperature

Spectral coverage: 1–700 μm (300000–430 GHz)

Objectives: identification of complex molecules in space, star birth and death etc.

New terahertz telescopes (II)

New terahertz telescopes (III)

ALMA (Atacama Large Millimeter/Submillimeter Array)

Global collaboration mission: East Asia, Europe, and North America

Location: Chile, 5000 meters above sea level

Operation: 2012 (50 years lifetime)

Telescope: a system up to 66 high-precision dish antennas

Spectral coverage: 300-9600 μm (1000–31 GHz)

Objectives: the physics of the cold Universe

Experiments at JPL

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H2O: 30 mTorr DC discharge: 400 mA, ~3 kV

Discharge

NH3

Sample cell

Pump

BeamsplitterRooftop reflector

FM

Rf Synthesizer Multiplier chain

PC

Si detector

Lock-in

×6×2

×3…

Source frequency: 400–1230, 1575–1626 GHz

Discharge cell: 1.2-meter-long

Static quartz cells for stable molecules

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Length = 1or 3 m

~100mm

Bomco 2.75" conflatquartz-to-metal seal

25-35 mm

15 o

3 mm thick flat quartz window

Leaking rate: ~1 mTorr/week

The 13 rejected microwave lines

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