There is a growing body of experimental evidence showing that the kinetics of nascent vapor produced during pulsed laser heating of metals cannot always be ascribed to the surface thermal conditions. Some investigators have proposed that the discharge of energetic (nonthermal) atoms from metals can involve light coupling to surface plasmons. This requires surface roughness to facilitate wave vector matching of laser light with surface electromagnetic excitation modes. If true, superthermal vaporization kinetics should disappear from time-of-flight measurements when an optically smooth surface is used. Unfortunately, maintaining such an ideal surface is infeasible on a solid target because each laser pulse introduces nanometer sized roughness through the process of melting and resolidification. We have investigated the nature of vaporization from a liquid Hg surface using a nanosecond laser emitting 5 eV photons. Surface tension of the liquid provides an optically smooth surface for this experiment. Nevertheless, we observe superthermal vaporization kinetics from liquid Hg. Yet, the shape of the energy distribution is Boltzmann (the thermal expectation), and the energy distribution does not demonstrate any quanta characteristic of vaporization mediated by an electronic excitation. [S0022-1481(00)01602-9]

Issue Section:
Heat Transfer in Manufacturing
Keywords:
mercury (metal), liquid metals, vaporisation, surface plasmons, laser beam effects, surface tension, Heat Transfer, Laser, Liquid Metals, Thermophysical, Vaporization
Topics:
Heating, Lasers, Temperature, Plasmons (Physics), Metals, Vapors
1.
Kim
,
H. S.
, and
Helvajian
,
H.
,
1991
, “
Threshold Level Laser Photoablation of Oxidized Aluminum (111)—Photoejected Ion Translational Energy Distributions
,”
J. Phys. Chem.
,
95
, No.
17
, pp.
6623
–
6627
.
2.
Hoheisel
,
W.
,
Vollmer
,
M.
, and
Trager
,
F.
,
1993
, “
Desorption of Metal Atoms With Laser Light—Mechanistic Studies
,”
Phys. Rev. B
,
48
, No.
23
, pp.
463
–
17
.
3.
Lee
,
I.
,
Callcott
,
T. A.
, and
Arakawa
,
E. T.
,
1993
, “
Desorption Studies of Metal Atoms Using Laser-Induced Surface-Plasmon Excitation
,”
Phys. Rev. B
,
47
, No.
11
, pp.
6661
–
6666
.
4.
Shea
,
M. J.
, and
Compton
,
R. N.
,
1993
, “
Surface-Plasmon Ejection of Ag+ Ions From Laser Irradiation of a Roughened Silver Surface
,”
Phys. Rev. B
,
47
, No.
15
, pp.
9967
–
9970
.
5.
Bennett
,
T. D.
,
Krajnovich
,
D. J.
, and
Grigoropoulos
,
C. P.
,
1996
, “
Separating Thermal, Electronic, and Topographic Effects in Pulsed Laser Melting and Sputtering of Gold
,”
Phys. Rev. Lett.
,
76
, No.
10
, pp.
1659
–
1662
.
6.
Elam
,
J. W.
, and
Levy
,
D. H.
,
1997
, “
Low Fluence Laser Sputtering of Gold at 532 nm
,”
J. Appl. Phys.
,
81
, No.
1
, pp.
539
–
541
.
7.
Kelly
,
R.
, and
Dreyfus
,
R. W.
,
1988
, “
On the Effect of Knudsen-Layer Formation on Studies of Vaporization, Sputtering, and Desorption
,”
Surf. Sci.
,
198
, No.
1–2
, pp.
263
–
276
.
8.
Kelly
,
R.
, and
Dreyfus
,
R. W.
,
1988
, “
Reconsidering the Mechanisms of Laser Sputtering With Knudsen-Layer Formation Taken Into Account
,”
Nucl. Instrum. Methods Phys. Res. B
,
32
, No.
1–4
, pp.
341
–
348
.
9.
Ritchie
,
R. H.
,
Manson
,
J. R.
, and
Echenique
,
P. M.
,
1994
, “
Surface-Plasmon-Ion Interaction in Laser Ablation of Ions from a Surface
,”
Phys. Rev. B
,
49
, No
4
, pp.
2963
–
2966
.
10.
Pines
,
D.
,
1956
, “
Collective Energy Losses in Solids
,”
Rev. Mod. Phys.
,
28
, No.
3
, pp.
184
–
198
.
11.
Lemberg
,
H. L.
,
Rice
,
S. A.
, and
Guidotti
,
D.
,
1974
, “
Surface Plasmons in Liquid Mercury: Propagation in a Nonuniform Transition Layer
,”
Phys. Rev. B
,
10
, No.
10
, pp.
4079
–
4099
.
12.
Bennett
,
T. D.
,
Grigoropoulos
,
C. P.
, and
Krajnovich
,
D. J.
,
1995
, “
Near-Threshold Laser Sputtering of Gold
,”
J. Appl. Phys.
,
77
, No.
2
, pp.
849
–
864
.
13.
Ritchie
,
R. H.
,
1973
, “
Surface Plasmons in Solids
,”
Surf. Sci.
,
34
, pp.
1
–
19
.
14.
Levich, V. G., 1962, Physicochemical Hydrodynamics, Prentice-Hall, Englewood Cliffs, NJ.
15.
Krajnovich
,
D. J.
,
1995
, “
Laser Sputtering of Highly Oriented Pyrolytic Graphite At 248 Nm
,”
J. Chem. Phys.
,
102
, No.
2
, pp.
726
–
743
.
16.
Bennett, T. D., and Krajnovich, D. J., 1997, “Dynamics of Surface Melting During Laser Processing of Materials,” ASME Proceedings of the 32nd National Heat Transfer Conference; ASME, New York.
17.
Touloukian, Y. S., 1970, Specific Heat: Metallic Elements and Alloys, IFI/Plenum, New York.
18.
Touloukian, Y. S., 1970, Thermal Conductivity: Metallic Elements and Alloys, IFI/Plenum, New York.
19.
Touloukian, Y. S., 1970, Thermal Expansion: Metallic Elements and Alloys, IFI/Plenum, New York.
20.
Choyke
,
W. J.
,
Vosko
,
S. H.
, and
O’Keeffe
,
T. W.
,
1971
, “
A Comparison of the Optical Properties of Single Crystal and Liquid Mercury in the Energy Range 0.5 to 8.25 eV
,”
Solid State Commun.
,
9
, No.
6
, pp.
361
–
367
.
21.
Zinov’yev, V. E., and V. P. Itkin, 1990, Metals at High Temperatures: Standard Handbook of Properties, Hemisphere, New York.
22.
Iida, T., and Guthrie, R. I. L., 1993, The Physical Properties of Liquid Metals, Clarendon, Oxford.
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