3 – 3.5 MIR CRDS 1 – 1.5 NIR CRDS 432 1 m -HV O2O2 N2N2 OH X a A B X X ~

3 – 3.5 MIR

CRDS

1 – 1.5 NIR

CRDS

4 3 2 1 m

-HV

O2N2

OH

X

aA

B

X

X~

SRS configuration

Ti:Sa ringcw laser

Ti:Sa Amplifier

Nd:YAG pulse laser

Raman Cell

PD

InGaAs orInSbDetector

Ring-down cavity with slit-jet(absorption length ℓ = 5 cm)

L = 67 cm

Vacuum Pump

1 m single passSRS750 ~ 900 nm

40 ~ 100 mJ ~ 40 MHz

ℓ

Nd:YAGcw laser

1st Stokes, ~ 1.3 m, ~ 2 mJ2nd Stokes, ~ 3 m, ~ 200 JSRS: 180 – 220 MHz

Experimental Apparatus

R ~ 99.995% @ 1.3 m ~ 99.96% @ 3 m

0

( )( )

L L

c c

(1 )R

Ti:Sa ringcw laser

Ti:Sa Amplifier

Nd:YAG pulse laser

Raman Cell

PD

InGaAs orInSbDetector

Ring-down cavity with slit-jet(absorption length ℓ = 5 cm)

L = 67 cm

Vacuum Pump

1 m single passSRS750 ~ 900 nm

40 ~ 100 mJ ~ 40 MHz

ℓ

Nd:YAGcw laser

1st Stokes, ~ 1.3 m, ~ 2 mJ2nd Stokes, ~ 3 m, ~ 200 JSRS: 180 – 220 MHz

Experimental Apparatus

S. Wu, P. Dupre and T. A. Miller, Phys. Chem. Chem. Phys. 8 (2006) 1682

SRS configuration

0

( )( )

L L

c c

(1 )R

R ~ 99.995% @ 1.3 m ~ 99.96% @ 3 m ~ 200 MHz @ NIR

Doppler ( slit jet ) ~ 100 MHz @ MIR

D. Anderson, S. Davis, T. Zwier andD. Nesbitt, Chem. Phys. Lett. 258 (1996)207

~ 200 MHz @ NIRDoppler ( slit jet ) ~ 100 MHz @ MIR

D. Anderson, S. Davis, T. Zwier andD. Nesbitt, Chem. Phys. Lett. 258 (1996)207

Ti:Sa ringcw laser

Ti:Sa Amplifier

Nd:YAG pulse laser

Raman Cell

PD

InSbDetector

Ring-down cavity with slit-jet(absorption length ℓ = 5 cm)

L = 67 cm

Vacuum Pump

1 m single passSRS750 ~ 900 nm

40 ~ 100 mJ ~ 40 MHz

ℓ

Nd:YAGcw laser

DFM configurationExperimental Apparatus

DFMunit

Nd:YAG pulse laser

1064 nm (9398 cm-1), ~ 150 mJ

~ 3.3 m, 600 J,DFM: < 70 MHz

0

( )( )

L L

c c

(1 )R

Doppler ( slit jet ) ~ 100 MHz @ MIR

D. Anderson, S. Davis, T. Zwier andD. Nesbitt, Chem. Phys. Lett. 258 (1996)207

Doppler ( slit jet ) ~ 100 MHz @ MIR

D. Anderson, S. Davis, T. Zwier andD. Nesbitt, Chem. Phys. Lett. 258 (1996)207

The Comparison of CH3 Spectra ( 3 band )

0

500

1000

0

500

1000

1500

2000

PQ1(2)

PQ1(1)

RR0(0)

PQ2(2)

RR1(1)

PR1(1)

3165.01 3165.44 3174.30 3175.43 3182.86 3203.30

3165.01 3165.44 3174.30 3175.43 3182.86 3203.30

Wavenumber (cm-1)

Abs

orb

ance

per

pas

s (

ppm

)

using SRS

using DFM

0.05 cm-1

370 MHz

150 MHz

240 MHz

105 MHz

Spectrum assignment according to:T. Amano, P. F. Bernath, C. Yamada, Y. Endo and E. Hirota, J. Chem. Phys. 77 (1982) 5284S. Davis, D. T. Anderson, G. Duxbury and D. J. Nesbitt, J. Chem. Phys. 107 (1997) 5661

KNK” (N”)

0 10 20

1

10

100

0 10 20

1

10

100

Non-exponential Decay

laser > = Doppler The beginning of the decay reflects

the medium absorption The end of the decay reflects the e

mpty cavity absorption

The non-linear response of the absorption medium The absorption is saturated at the v

ery beginning of the decay The later part of the decay is appro

ximated by the linear absorption

The chemical or physical dynamics faster than Multi-exponential decay To analyze the decay as a function

of time

t (s)

Intr

acav

ity E

nerg

y ( J

)

Empty cavity

CH3 [ RR

0 (0) ] absorptionEmpty cavityC

H3 [ RR

0 (0) ] absorption

SRSradiation

DFMradiation

Decay curve @ 3174.295 cm-1

= 1.7 s (99.63%)0 = 5.8 s (99.95%)

= 1.0 s (99.98%)0 = 5.9 s (99.99%)

Spectra of Jet- Cooled CRDS (DFM version)

0

500

1000

1500

2000

0 20 40 60 80

0.01

0.1

1

10

P, Q and R branch of 3 band of methyl radical (CH3)A

bso

rba

nce

pe

r p

ass

(p

pm

) RR0(0)

RR1(1)

RR2(2)

RR3(3)PR1(1)

PQ1(1)PP1(1)

PP2(2)PP3(3)

3128.55 3137.56 3146.50 3165.44 3174.30 3182.86 3191.34 3199.74 3203.30

0.05 cm-1

3127 3167 3207

Wavenumber (cm-1)

Erot (cm-1)

T = 19 (2) K

I /

Ho

nl-

Lon

do

n F

ac.

Wavenumber (cm-1)

Ab

sorb

an

ce p

er

pa

ss (

pp

m)

3038 3040 3042 3044 3046 3048

0

100

200 R branch 1 (K=0) band of ethyl radical (C2H5)

0 10 20 30

0.1

1

I /

Ho

nl-

Lon

do

n F

ac.

Erot (cm-1)

T = 18 (2) K

0

1

23

45

67

Spectrum assignment according to: S. Davis, D. Uy and D. J. Nesbitt, J. Chem. Phys. 112 (2000) 1823

KNK” (N”)

DischargeExpansions

- HV

-HV

Longitudinal Discharge Transverse Discharge

RR0(0)3 band

CH3I

CH3

I

Ne

Ne

peak absorbance per pass( 200 mA discharge )

1800 ppm 1700 ppm

Max. stable discharge current200 mA

(1800 ppm)

400 mA

(2000 ppm)

Noise

( at max. discharge current )7 ppm 5 ppm

S/N ~ 400S/N ~ 400S/N ~ 250S/N ~ 250

DischargeExpansions

- HV

Longitudinal Discharge Transverse Discharge

CH3I

CH3

I

Ne

Ne

RR0(0)3 band

peak absorbance per pass( 200 mA discharge )

1800 ppm 1700 ppm

Max. stable discharge current200 mA

(1800 ppm)

400 mA

(2000 ppm)

Noise

( at max. discharge current )7 ppm 5 ppm

Downstream injection No Yes

O2

O2

O2

-HV

S/N ~ 400S/N ~ 400S/N ~ 250S/N ~ 250

Main Reactions Related to CH3, O2 and

O

O2

CH3 I

Ne

Reactions Products

2980 2990 30000

200

4000

2

4

Wavenumber (cm-1)

S

x 10

-20 cm

)

I (p

pm)

2850 2950 3050 3150 3250Wavenumber (cm-1)

Number density (1013 cm-3)CH3 1.2

C2H6 0.30

CH4 0.010

CH3 0.12

C2H6 0.048

CH2O 0.79

Wit

ho

ut

O2

Wit

h O

2

10

mm 0.8 mm

CH3OO 0.15

O2

A. Perrin, A. Valentin, L. Daumont, J. Mol. Struc. 780–781 (2006) 28

CH3 I

Ne

CH3I

Downstream Injection

Wit

ho

ut

O2

Wit

h O

2

Number density (1013 cm-3)CH3 0.96 ↓0.24

C2H6 0.42 ↑0.12

CH4 0.015 ↑0.005

CH3 0.36 ↑0.24

C2H6 0.05 ↑0.012

CH2O 0.0 ↓0.79

10

mm 0.8 mm

RR0(0)3 band

Ab

sorb

an

ce (

pp

m)

Wavenubmer (cm-1)

0 100 200 3000

500

1000

1500

2000

time (s)

Ab

sorb

an

ce (

pp

m)

N2 or Ne injection

O2 injection

25%

CH3OO 0.3 ↑0.15

O2

or

N2 NeO2

Ne

7385 73900.0

0.5

0.0

0.5

1.00.0

0.5

1.00

5

10

Candidate for Jet-cooled spectra of CH3OO at NIR

Wavenumber (cm-1)

Abs

orpt

ion

per

pass

(p

pm)

Prediction at 20 K

CH3I as precursorO2 downstream inject.Scan #1

Scan #2

CH3COCH3, as precursorO2 downstream inject.

Conclusion & Further work

NIR (1.0 – 1.5 m) & MIR (3.0 – 3.5 m) spectra region Near Doppler limited resolution (~200 MHz @ NIR, <70 MHz @ MIR)

High sensitivity (0.7 x 10-7 Hz-1/2 @ NIR and 1.1 x 10-6 Hz-1/2 @ MIR)

Transverse discharge with capability of downstream injection Candidate for jet-cooled spectra of CH3OO was found in NIR

Rotational structure of CH3OO Other interesting radicals…

AcknowledgementDr. Terry A. MillerCurrent group members: Patrick Rupper, Gabriel Just, Jinjun Liu, Erin Sharp, Ilias Sioutis and Becky Gregory.Former group members: John Yi and Vadim Stakhursky

&Group in mechanical engineering: Dr. J. William Rich, Dr. Igor V. Adamovich, Yurii Utkin

&Colleagues in machine shop: Jerry Hoff, Larry Antal, Joshua Shannon

Colleagues in electronic shop: Dale Karweik, John Sullivan

&

NSF Funding

Discharge Expansions1)

2)

3)

10 mm

5 mm

7320 7360 7400 74400

300

600

7320 7360 7400 74400

300

600

7360 7370 7380 7390 74000

5

10

Wavenumber (cm-1)

Ambient CRDS experiment of CH3OO

JCP. 112 (2000) 10695

Simulation

Doppler = 0.2 cm-1

T = 293 K

Simulated Jet-Cooled CRDS of CH3OO

= 0.01 cm-1

T = 20 K

Nobs ~ 1.5 x 1015 cm-3

labsorption ~ 16 cm

CH3OO in the NIR …

Abs

orba

nce

per

pass

(pp

m)

Sband = 3.7 x 10-19 cm / mol.