Abstract

Some effects arising from the interaction of TEA CO2 laser pulses with individual aerosol particles are described. The time dependence of thermal radiation emitted from aerosol particles heated with pulses from a TEA laser is shown to be related to the size of individual particles and to the distribution of sizes within an aerosol. Charge and mass changes have been determined for single particles on absorption of 10.6-μm CO2 laser radiation. The predominant charging effect at low intensities (≃ 105 W/cm2) involves a loss of positive charge. Splitting of particle aggregates has also been observed.

© 1976 Optical Society of America

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References

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  1. D. Lencioni, Appl. Phys. Lett. 23, 12 (1973).
  2. R. T. Brown, D. C. Smith, J. Appl. Phys. 46, 402 (1975).
  3. D. C. Smith, R. T. Brown, J. Appl. Phys. 46, 1146 (1975).
  4. R. W. Weeks, W. W. Duley, J. Appl. Phys. 45, 4661 (1974).
  5. W. Kunkel, Rev. Sci. Instrum. 21, 4 (1950).
  6. J. Bryant, Combust. Flames 20, 138 (1973).
  7. H. Lamberton, P. Pearson, IEEE J. Quantum Electron. QE-8, 145 (1972).
  8. R. W. Weeks, Ph.D. Thesis, York University (1975).

1975 (2)

R. T. Brown, D. C. Smith, J. Appl. Phys. 46, 402 (1975).

D. C. Smith, R. T. Brown, J. Appl. Phys. 46, 1146 (1975).

1974 (1)

R. W. Weeks, W. W. Duley, J. Appl. Phys. 45, 4661 (1974).

1973 (2)

J. Bryant, Combust. Flames 20, 138 (1973).

D. Lencioni, Appl. Phys. Lett. 23, 12 (1973).

1972 (1)

H. Lamberton, P. Pearson, IEEE J. Quantum Electron. QE-8, 145 (1972).

1950 (1)

W. Kunkel, Rev. Sci. Instrum. 21, 4 (1950).

Brown, R. T.

R. T. Brown, D. C. Smith, J. Appl. Phys. 46, 402 (1975).

D. C. Smith, R. T. Brown, J. Appl. Phys. 46, 1146 (1975).

Bryant, J.

J. Bryant, Combust. Flames 20, 138 (1973).

Duley, W. W.

R. W. Weeks, W. W. Duley, J. Appl. Phys. 45, 4661 (1974).

Kunkel, W.

W. Kunkel, Rev. Sci. Instrum. 21, 4 (1950).

Lamberton, H.

H. Lamberton, P. Pearson, IEEE J. Quantum Electron. QE-8, 145 (1972).

Lencioni, D.

D. Lencioni, Appl. Phys. Lett. 23, 12 (1973).

Pearson, P.

H. Lamberton, P. Pearson, IEEE J. Quantum Electron. QE-8, 145 (1972).

Smith, D. C.

R. T. Brown, D. C. Smith, J. Appl. Phys. 46, 402 (1975).

D. C. Smith, R. T. Brown, J. Appl. Phys. 46, 1146 (1975).

Weeks, R. W.

R. W. Weeks, W. W. Duley, J. Appl. Phys. 45, 4661 (1974).

R. W. Weeks, Ph.D. Thesis, York University (1975).

Appl. Phys. Lett. (1)

D. Lencioni, Appl. Phys. Lett. 23, 12 (1973).

Combust. Flames (1)

J. Bryant, Combust. Flames 20, 138 (1973).

IEEE J. Quantum Electron. (1)

H. Lamberton, P. Pearson, IEEE J. Quantum Electron. QE-8, 145 (1972).

J. Appl. Phys. (3)

R. T. Brown, D. C. Smith, J. Appl. Phys. 46, 402 (1975).

D. C. Smith, R. T. Brown, J. Appl. Phys. 46, 1146 (1975).

R. W. Weeks, W. W. Duley, J. Appl. Phys. 45, 4661 (1974).

Rev. Sci. Instrum. (1)

W. Kunkel, Rev. Sci. Instrum. 21, 4 (1950).

Other (1)

R. W. Weeks, Ph.D. Thesis, York University (1975).

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Figures (11)

Fig. 1
Fig. 1

Schematic of system used for studying the interaction of TEA CO2 laser pulses with particles in an aerosol.

Fig. 2
Fig. 2

Schematic of interaction region in Fig. 1.

Fig. 3
Fig. 3

Time dependence of visible light emission from a monodisperse aerosol of alumina particles with a = 0.15 μm. The upper curve was recorded 1 h after formation of the aerosol, while the next two curves are for 2 h and 3 h, respectively. The lower trace shows the laser pulse.

Fig. 4
Fig. 4

Relative emission from the above aerosol normalized to unity at zero time for times up to 2 h following creation.

Fig. 5
Fig. 5

Variation of visible emission with particle radius in two monodisperse alumina aerosols.

Fig. 6
Fig. 6

Experimental light emission traces from fine thermal and medium thermal carbon black aerosols heated with pulses from a TEA CO2 laser. — — —Theoretical fit obtained from manufacturer’s distribution of particle sizes.

Fig. 7
Fig. 7

Light emission traces from a large aggregate of carbon black and its components after deaggregation by a laser pulse.

Fig. 8
Fig. 8

(a) Alimina particle of 1.2-μm radius changes from positive to negative charge when a 10.6-μm pulse passes through chamber. (b) Similar trace with a neutral particle becoming negatively charged and a negatively charged particle becoming more negative after interaction.

Fig. 9
Fig. 9

Histogram of charge change behavior for alumina aerosol particles.

Fig. 10
Fig. 10

Positively charged 1.6-μm radius alumina particle splits into several negative components when heated with CO2 laser pulse. (b) Negatively charged 2.1-μm radius particle splits into negatively and positively charged particles.

Fig. 11
Fig. 11

Plot of average total charge change in a given size range QTOT vs radius for negative to more negative events.

Equations (3)

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T ( t ) = T g + F 0 γ 4 [ A exp ( - λ 1 t ) γ 2 - λ 1 + b exp ( - λ 2 t ) γ 2 - λ 2 - exp ( - γ 2 t ) ( A γ 2 - λ 1 + B γ 2 - λ 2 ) ] ,
F ( t ) = F 0 [ A exp ( - λ 1 t ) + B exp ( - λ 2 t ) ] .
R [ λ , T ( t ) ] d λ = c 1 d λ λ 5 { exp [ c 2 ( λ T ) - 1 ] } ,

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