2p photon yield (p, t, humidity) = ?

Temperature dependence of the

quenching of N2(C 3Πu, v’ = 0, 1) by

N2(X) and O2(X)

L. Pereira1, A. Morozov1,2, M. M. Fraga1, T. Heindl2, R. Krücken2, J. Wieser3 and A. Ulrich2

1 LIP-Coimbra, Departamento de Física, Universidade de Coimbra, 3004-516 Coimbra, Portugal. 2 Physik Department E12, Technische Universität München, 85748 Garching, Germany.

3 Coherent GmbH, Zielstattstrasse 32, 81379 München, Germany.

6th fluorescence workshop, L’Aquila, 2009

L . Pereira

2P photon yield (P, T, humidity) = ?

Direct measurements ‘’3D’’ exp. data

Kinetic model

Only electron impactexcitation:Partial parameterization, with the p’

Measurement of the quenching rates


L . Pereira

To measure the Kq N2( C 3Πu, v = 0, 1) by N2(X)and O2(X) we use:

Time resolved optical spectroscopy

Effective decay rate, Reffkq

Excitation method Pulsed12 KeV electron beam

High S/B

Gas purity

High statistics


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e-gun

Stainless steel chamber Cooling head inside

S20 PMT Monochromator

PC

Set up at the Technische Universität München


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Electric valves

PT100

MgF2 window

Ceramic foil

Cooling head


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Results


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N2 wavelength spectra @ 400 hPa

Spectra recorded at the central wavelength ofthe bands with 1 nm resolution assure negligible contribution of the adjacent bands.


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Time spectra, 2P(0,0) [337,1 nm]

C = C0+Me-Reff t

Non - monoexponential (VR)

After pulses from PMT

Fitted range


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0 20 40 600.1

1

10

N2, 200 hPa

Simulation, v' = 0 Simulation, v' = 1 Fit to Sim. v' = 0 Fit to Sim. v' = 1

diff. + 2.4%

diff. = + 0.7%

Co

un

ts,

10

10

Time, ns

0 20 40 60 80 1000.1

1

10 Simulation, v' = 0 Simulation, v' = 1 Fit to Sim. v' = 0 Fit to Sim. v' = 1

diff. = + 2.5%

N2, 100 hPa

Co

un

ts,

10

10

Time, ns

diff. = + 3.3%

Effect of the vibrational relaxation on the fitting method

Rel. exc. efficiencies from A. Morozov et al. Eur., Phys. J. D 33, 207–211 (2005).V.R. and quenching rates from G. Dilecce et al. / Chemical Physics Letters 431 (2006) 241–246.


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Pressure limits

500 hPa for v’ = 0

250 hPa for v’ = 1

~ 5 ns effective lifetime

Instrumental factors

Fitting method

e.g. 200 hPa N2 + 10 hPa O2

e.g.‘’dry air’’ 85 hPa total pressure

Pure N2

N2/O2 mixturesv’ = 0


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Pure nitrogen


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Effective decay rate v’ = 0, 1 vs. pressure at room temperature (298 K)

0 100 200 300 400 5000.00

0.04

0.08

0.12

0.16

0.20

0.24 r1 = (2.92 0.16)107s-1

k1 = (2.680.06)10-11cm3s-1

p'1 = 44.9 3.1 hPa

2P(0,0) 2P(1,0)

Eff

ectiv

e de

cay

rate

, ns

-1

N2 pressure, hPa

r0=(2.79 0.16)107s-1

k0=(1.250.04)10-11cm3s-1

p'0 = 91.6 7.7 hPa


L . Pereira

Effective decay rate v’ = 0, 1 vs.

temperature

205 225 245 265 285 305

0.08

0.12

0.16

0.20

0.24

300 hPa 200 hPa 100 hPa

Eff

ectiv

e de

cay

rate

, ns

-1

Temperature, K

v' = 1

205 225 245 265 285 305

0.12

0.16

0.20 v' = 0 500 hPa 400 hPa 300 hPa

Eff

ectiv

e de

cay

rate

, ns

-1

Temperature, K


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205 225 245 265 285 305

0.12

0.16

0.20 v' = 0 500 hPa 400 hPa 300 hPa

Eff

ectiv

e de

cay

rate

, ns

-1

Temperature, K


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205 225 245 265 285 305

0.08

0.12

0.16

0.20

0.24

300 hPa 200 hPa 100 hPa

Eff

ectiv

e de

cay

rate

, ns

-1

Temperature, K

v' = 1


L . Pereira

Quenching rates vs. temperature, v’ = 0

Ref.* A. Morozov et al. Eur., Phys. J. D 46, 51–57 (2008).

k(T)=k0(T/300)β

M.M. Fraga et al. NIM A 597 (2008) 75–82

β = - 0.37 ± 0.15

M.M. Fraga et al. NIM A 597 (2008) 75–82 205 225 245 265 285 305

0.0

0.4

0.8

1.2

1.61.2

1.3

1.4

1.5

k 0, 10-1

1 c

m3

s-1

Temperature, K

500 hPa 400 hPa 300 hPa 200 hPa 150 hPa 100 hPa From S-V plot Ref.*

k0 = (1.24 ± 0.4)×10-11(cm3s-1)

β = - 0.33 ± 0.06


L . Pereira

Quenching rates vs temperature, v’ =1

Ref. *A. Morozov et al. Eur., Phys. J. D 46, 51–57 (2008).

k1(T) = (2.25 ± 0.21) ×10-11 + (1.41 ± 0.78)×10-14×T

205 225 245 265 285 3050.0

0.5

1.0

1.5

2.0

2.5

3.0

2.4

2.6

2.8

k 1, 10

-11 c

m3 s-1

Temperature, K

50 hPa 100 hPa 200 hPa From S-V plot Ref.*


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k0 increases by 13 ± 3 % in the range 300 down to 210 K.

k1 decreases by 5 ± 2.5 % in the range 300 down to 210 K.

Is it vibrational relaxation of v’ = 1 responsible for this difference?


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Nitrogen/Oxygen mixtures


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Effective decay rate v’ = 0 vs. O2 pressure at room temperature (298 K)

0 2 4 6 8 10 12 140.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

k = (30.5 ± 2) × 10-11 cm3s-1

p' air

= 15.6 ± 1.2 hPa

Eff

ectiv

e de

cay

rate

, ns

-1

Oxygen pressure, hPa

PN

2

= 150 hPa

p’ air = 15.89 ± 0.73 hPa

M. Ave et al. NIM A 597 (2008) 41-45


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220 240 260 280 300

0.170

0.175

0.180

0.155

0.160

0.165

0.1600.1650.1700.1750.1550.1600.1650.1700.175

Dry air, 85 hPaEffe

ctiv

e d

eca

y ra

te, n

s-1

Temperature, K

100/15 hPa

150/12.5 hPa

200/10 hPa

Effective decay rate v’ = 0 vs. temperature for several N2/O2 mixtures


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220 240 260 280 3000.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Air 85 hPa

Eff

ect

ive

de

cay

rate

, n

s-1

Temperatura, K


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Temperature dependence of the quenching rate constant

( ) N2k-=2O

2N02O N

N)T(r-)T(RTk

KN2(T) = 1.24 ×10-11 (T/300)-0.33 cm3s-1r0 = 0.0279 ns-1


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210 220 230 240 250 260 270 280 290 3000

4

8

12

16

20

24

28

32

24

28

32

36

k O2,

10-1

1 cm

3 s-1

Temperature, K

O2/N

2, hPa

200 / 10 150 / 12.5 100 / 15 67.15 / 17.85 (85 hPa air) from Fig. 2

kO2(T) = (25.7 ± 0.2) ×10-11 + (13 ± 6)×10-14×T


L . Pereira

The quenching rate constant of the N2(C 3Πu,v’ = 0)

state by O2(X) decreases by (4 ± 2)% in the in the

range 300 down to 210 K.


L . Pereira

In the following talk by M.M. Fraga these results will be used to evaluate the temperature dependence of the emission intensity in N2 and N2/O2 mixtures

Thank you for your attention !

2p photon yield (p, t, humidity) = ?

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