Fluorescence studies using low energy electron beam excitation

Technische Universität München

Fluorescence studies using low energy electron beam excitationa very personal view by

Andreas Ulrichwith real work done by:

Thomas Dandl, Thomas Heindl, and Andrei Morozov*

and a lot of help by

Jochen Wieser**

Physik Department E12Technische Universität München

*University of Coimbra**Optimare Analytik GmbH & Co KG

Air Fluorescence Workshop, Karlsruhe 2011

[email protected]


A. Ulrich et al., Air Fluorescence, Karlsruhe 2011

Spectroscopy:Provides information about the species involved

We work with beams in nitrogen and in air



PMT

GratingVacuumMonochromator

1/5 Mirror Optics

Ti Gas Purifier

Gas Cell

Faraday Cup

Beam Line Vacuum

FiberOptics

Ocean Opt.Spectrometer

Heavy ion beam experiments at the Munich 15 MV Tandem accelerator:



100 MeV 32S beam stopped in neon



200 400 600 800 1000

0

10000

20000

30000

40000

50000

60000

70000

Inte

nsity

(nm)

e-beam, 5µA

Pure nitrogen, 800mbar

Some information comes from emission spectra



200 400 600 800 1000

0

10000

20000

30000

40000

50000

60000

70000

Inte

nsity

(nm)

600 800 1000

0

10000

Inte

nsity

(nm)

Gaydon Herman green (GHG)and Herman Infrared (HIR)

280 300 320 340 360 380 400 420

0

10000

20000

30000

40000

50000

60000

70000

Inte

nsity

(nm)

N2

200 220 240 260 280 300

0

1000

2000

3000

4000In

tens

ity

(nm)

NO200-300nm

500-1000nm

280-420nm



Extension into the VUV shows N I lines ! (nitrogen spectrum)



Atomic nitrogen shows up in the VUV spectral range



0 1 2 3 4 5 6 7 8 90,0

0,2

0,4

0,6

0,8

1,0

Rat

io

Beam Current (A)

NO / N2 GHG / N2

200 300 400 500 600-2000

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

Inte

nsity

(nm)

1A beam current 8A beam current(scaled on 337nm)

N2 / NO 337nm/247nmN2 / GHG 337nm / 557nm

The spectrum depends on beam current!

Plasma effects and radiation trapping



200 300 400 500 600

0

2000

4000

6000

8000

10000

12000

14000

Inte

nsity

(nm)

pure NitrogenNitrogen with 0,1% Oxygen

e-beam 1µA

1000mbar gas

Huge effect of O2



0 5 10 15 20 25 3020000

25000

30000

35000

40000

Inte

nsity

at 3

37nm

(a.u

.)

Time (min)

Stopping the gas flow: 17% in 30min



200 300 400 500 600

0

10000

20000

30000

40000

50000

60000

70000

200 225 250 275 300

0

500

1000

1500

Inte

nsity

(nm)

600 700 800 900 1000

0

1000

2000

Inte

nsity

(nm)

Inte

nsitä

t

[nm]

5A 400mbar fresh5A 400mbar after 1min

Appearance of CN

600nm 1000nm



200 300 400 500 6000

1000

2000

3000

4000

5000

6000In

tens

ity

(nm)

Nitrogensynth. Air(scaled on 337nm)

e-beam, 8µA

800mbar gas



200 250 300 350 400 450 500 550 6000

2000

4000

6000

8000

10000

12000

14000

16000In

tens

ity

(nm)

NitrogenAir(scaled on 337nm)

e-beam, 8µA800mbar gas



Qualitative results from spectroscopy:Pure nitrogen is very sensitive to impurities

NO is often formed

Higher lying bands are populated (cascades ?)

Nitrogen is split to N atoms even excited N atoms

Regular air and synthetic air behave differently

Next step:

relative sensitivity calibration



Thomas Dandl has used 3 types calibration lamps:

Halogen Lamp (LOT)

Wi 17G (Osram) 2x

Deuterium Lamp (LOT, Cathodeon) one lamp, 2 data sets

to measure the relative response of an Ocean Optics QE65000 between 280 and 420nm

He used (in part) filters for the wavelength region to suppress stray light



Setup for calibration

Calibration lamp

Gas cell

MgF2 windows

12 keV electron source

Fiber optics entrance



200 400 600 800 10000,0000

0,0005

0,0010

0,0015

0,0020

0,0025

0,0030

corre

ctio

n fu

nctio

n

(nm)

Wi17/G 2892Wi17/G 3261Halogenlamp



280 300 320 340 360 380 400 4200,00

0,25

0,50

0,75

1,00

1,25

Rat

io

(nm)

fiber rotated 1fiber rotated 2fiber bentfiber tilted

Important message: Do not touch the setup after calibration !



260 280 300 320 340 360 380 400 4200,0000

0,0005

0,0010

0,0015

0,0020

0,0025

0,0030

0,0035

0,0040

Wi17/G 2892Wi17/G 3261Deuterium lamp (not our lamp)Deuterium lamp (our lamp)Halogen lamp

corr

ectio

n fu

nctio

n

(nm)

solid line: with UG11-filter

dashed line: without UG11-filter



300 320 340 360 380 400 420-200

0

200

400

600

800

1000

1200

1400

1600

1800

-30

-25

-20

-15

-10

-5

0

5

10

15

20

Inte

nsity

(a.u

.)

(nm)

Laborluft M.Ave et al.

per

cent

age

wis

e de

viat

ion

from

syn

th. a

ir

synth. Air



200 250 300 350 400 450 500 550 600

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

-320

-280

-240

-200

-160

-120

-80

-40

0

40

80

120

160

800mbar400mbar100mbar

Inte

nsity

(nm)

per

cent

age-

wis

e de

viat

ion

from

800

mba

r dat

a

Pure nitrogen, 8μA



0 200 400 600 800 100061

62

63

64

65

66

67

68

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Pressure [mbar]

357,7nm

0 200 400 600 800 100022,0

22,2

22,4

22,6

22,8

23,0

23,2

23,4

23,6

23,8

380,5nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]0 200 400 600 800 1000

7,2

7,3

7,4

7,5

7,6 405,0nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]

0 200 400 600 800 100016

18

20

22

24

26357,7nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]

0 200 400 600 800 100011

12

13

14

15

16353,7nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]0 200 400 600 800 1000

8,5

9,0

9,5

10,0

10,5

11,0

11,5

12,0

12,5

13,0

375,6nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]0 200 400 600 800 1000

3,2

3,4

3,6

3,8

4,0

4,2

4,4

4,6

4,8

5,0

399,8nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]

0 200 400 600 800 10002,3

2,4

2,5

2,6

2,7

2,8

328,5nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]0 200 400 600 800 1000

3,0

3,2

3,4

3,6

3,8

4,0

4,2

4,4

371,1nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]0 200 400 600 800 1000

3

4

5

6

7

8

9

391,4nm

Inte

nsitä

t bez

ogen

auf

337

,1nm

[%]

Druck [mbar]

I (p) various lines relative to the 337nm line 100 to 1000mbar

5 to 10% starting at vib. level 0 ???

30 to 50% at vib. Level 1

N2+ 100%15% level 3 30% level 2

Pressure dependence rel. to 337nm line



0 1 2 3 4 5 6 7 8 957

58

59

60

61

62

63

64

65

66

Inte

nsitä

t

357,7nm

0 1 2 3 4 5 6 7 8 9

20,5

21,0

21,5

22,0

22,5

23,0

23,5

Inte

nsitä

t

380,5nm

0 1 2 3 4 5 6 7 8 9

6,6

6,8

7,0

7,2

7,4

7,6

Inte

nsitä

t

405nm Beam current dependence of some lines in pure nitrogen normalized to the 337nm line

Quenching by free electrons?

5%

0 to 9 µA



200 250 300 350 400 450 500 550 600

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

-45

-40

-35

-30

-25

-20

-15

-10

-5

0

5

8A4A1A

Inte

nsity

(nm)

per

cent

age

wis

e de

viat

ion

from

int a

t 8A



Conclusion:Spectroscopy provides a lot of information about the nitrogen fluorescence.

Calibration measurements have to be carefully prepared.

Relative intensity measurements of the emission bands would have to be repeated with better wavelength resolution.



Thank you for your attention !

Fluorescence studies using low energy electron beam excitation

Documents

Transcript of Fluorescence studies using low energy electron beam excitation