First results from the far-infrared beamline at the Canadian Light Source: High resolution analysis of acrolein in the 600 cm-1 regionA.R.W. McKellar National Research Council of CanadaD.W. Tokaryk, L.-H. Xu University of New BrunswickD.R.T. Appadoo, T. May Canadian Light Source

Centre for Laser, Atomic, and Molecular SciencesUniversity of New Brunswick

First results from the far-infrared beamline at the Canadian Light Source: High resolution analysis of acrolein in the 600 cm-1 regionA.R.W. McKellar National Research Council of CanadaD.W. Tokaryk, L.-H. Xu University of New BrunswickD.R.T. Appadoo, T. May Canadian Light Source

Canadian Light Source Saskatoon, Saskatchewan

Where is Saskatoon?

CLS ParametersEnergy: 2.9 GeVCurrent: 200 mACircumference: 171 m12 straight sections, 5.2 m longRF: 500 MHz, 2.4 MV, supercon Injection: 250 MeV LINAC

full energy booster ringMain building: ~ 85 x 85 m

Synchrotron IR

There are two infrared beamlines at CLS:1) Far IR (this talk)2) Mid IR spectromicroscopy (biological / industrial samples)

All other CLS beamlines are for x-raysThe synchrotron simply replaces the normal source (globar), providing

continuum IR radiation to a conventional FTIR spectrometer

The high brightness of synchrotron radiation is ideal for the small entrance aperture required for high spectral resolution

Bruker IFS 125 HR spectrometer: max optical path difference = 9.4 m; instrumental resolution ~ 0.0008 cm-1 (24 MHz)

50 100 150 200 250 300 350

050

010

0015

0020

0025

0030

0035

0040

00Tr

ansm

ittan

ce [%

]

Energy / cm-1

SR23

SR27

Hg

SR27/Hg

SR23/Hg (SR is normalized to 202 mA)

SR23: Synch. Radiation Run 23SR27: Synch. Radiation Run 27Hg: internal Hg lamp

Synchrotron brightness advantage (the good news)

100 150 200 250 300 350Wavenumber cm-1

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

Sing

le c

hann

el

SR23

Hg

Synchrotron noise (the bad news)

Clearly signal-to-noise ratio is the important factorOur problem is mechanical vibrations in the optics that bring IR radiation from the storage ring to the spectrometer

Ring Source

Diamond Window

Spectrometer

Shielding Wall

With successive improvements, the synchrotron now has a significant advantage over the globar from 250 ~ 800 cm-1

But we are aiming for much better performance• Reduce noise at source: better isolation of offending

cooling pumps, heat exchangers, pipe runs, etc.• Reduce noise at beamline: more isolation, better

mounting of mirrors• Active optics to stabilize the input radiation on the

spectrometer aperture

AcroleinCH2CHCHO

Ene

rgy

/ cm

-1

0

100

200

300

400

500

600

181

182

184

131

171

121

Low-lying vibrational states of acrolein (propenol)

183

A 1.57955

B 0.15542

C 0.14152

• fundamental 8-atom species• planar near-prolate asymmetric rotor • interstellar molecule• combustion byproduct

(cigarette smoke)• potent respiratory irritant (smog)

17 band of acrolein, CH2CHCHO

Ka = 7 – 6Q-branch

nominal resolution 0.0012 cm-1

Wavenumber / cm-1

611.3 611.4 611.5 611.6 611.7

Abs

orba

nce

0.0

0.2

0.4

0.6

0.8

Synchrotron, 32 scans

Globar, 300 scans

Synchrotron, 414 scans

Wavenumber / cm-1

592.6 592.8 593.0 593.2 593.4

Abs

orba

nce

-0.5

0.0

0.5

1.0

1.5

302520

20253035

35pQ1(J)

rQ0(J)

*

Acrolein: center of the 17 band

Acrolein: qQ-branch, center of the 12 band

Wavenumber / cm-1

563.4 563.6 563.8 564.0 564.2 564.4

Abs

orba

nce

-0.2

0.0

0.2

12 band

17 band

12131415 246811 10 916

Wavenumber / cm-1

628.2 628.4 628.6 628.8

Abs

orba

nce

0.0

0.2Ka = 13 - 12 Q-branch

Angular Momentum, J

15 20 25 30 35 40 45

Obs

- C

alc

/ cm

-1

-0.08

-0.06

-0.04

-0.02

0.00

0.02

0.04

0.06

0.08

Ka' = 13

Acrolein: local perturbation of 17 Ka = 13 levels around J = 30,

explained by crossing with Ka = 13 of 418

12 17 418 Ground state

v0 564.3404(1) 593.0793(1) 621.958(16)

A 1.5789146(15) 1.5768182(12) 1.384325(23) 1.57954976

B 0.1553289(44) 0.1552016(44) 0.1562836(42) 0.155424164

C 0.14136381(15) 0.14150373(10) 0.1436751(42) 0.141520893

105 x DK 1.23410(33) 1.18322(26) -8.303(57) 1.20053

107 x DJK -3.2434(74) -2.8887(20) -2.92953 -2.92953

108 x DJ 3.4938(71) 3.5101(30) 3.47417 3.47417

107 x K 2.18(17) 2.09(10) 1.9342 1.9342

109 x J 3.855(63) 3.917(33) 3.99773 3.99773

1010 x HK -7.827(49)

Ga(12,17) 0.251076(75)

Gb(12,17) 0.0454(14)

105x Z1(12,17) -6.039(37)

104x Z3(12,17) -4.29(68)

103x Ga(17,184) 6.533(24)

107x Z5(17,184) -4.17(25)

Acrolein: ~2000 lines of the 12 & 17 bands represented in terms

of 25 parameters (including ‘dark’ state 418)

10 20 30 40-0.02

-0.01

0.00

0.01

0.02

Angular Momentum, J

10 20 30 40

Obs

- C

alc

/ cm

-1

-0.03

-0.02

-0.01

0.00

0.01

0.02

0.03

Ka' = 8

Ka' = 14

Acrolein: local perturbations of Ka = 8 and 14 levels of 17 remain unexplained

Wavenumber / cm-1

613.9 614.0 614.1 614.2 614.3 614.4 614.5

Abs

orba

nce

0.0

0.1

0.2

0.3

0.4

0.5

Ka = 8 - 7 Q-branch

Ene

rgy

/ cm

-1

0

100

200

300

400

500

600

181

182

184

131

171

121

Low-lying vibrational states of acrolein (propenol)

183

Acrolein: recently we also studied the 18 fundamental band at 158 cm-1

0.0

0.5

1.0

Wavenumber / cm-1

158.0 158.2 158.4 158.6 158.8

Intensity / arbitrary units

0

1

2

3

4

synchrotron source2.4 hours

globar source7.1 hours

Acrolein 18 central region

Wavenumber / cm-1

157.8 158.0 158.2 158.4 158.6 158.8

Absorbance

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8 H2O impurity

simulated spectrum

observed spectrum

Acrolein 18 central region

18 Ground state*

v0 157.8835(1)

A 1.5271603(10) 1.57954976

B 0.15564972(21) 0.155424164

C 0.14208563(17) 0.141520893

105 x DK -0.2143(8) 1.20053

107 x DJK -2.890(8) -2.92953

108 x DJ 3.642(7) 3.47417

107 x K -0.08(20) 1.9342

109 x J 4.11(5) 3.99773

109 x HK -7.944(28)

1010 x HKJ 6.6(31) -0.1586

1012 x LK 2.824(27)* Winnewisser, Winnewisser, Honda, & Hirota, Z. Naturforsch. 30a, 1001 (1975)

Acrolein 18 parameters

High-resolution synchrotron IRPrevious results from MAXlab and LURE were promising -- we hope to do better

Presently at CLS:100 – 200 cm-1 region: SR is ~ 4 times better250 – 700 cm-1 region: SR is ~ 8 times better

Other new synchrotrons (SOLEIL, Australia, Switzerland, Singapore, ...) are building hi-res IR facilities

Are we the first synchrotron user facility for high-resolution IR spectroscopy of gases ?