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`(cid:100)(cid:346)(cid:349)(cid:400)(cid:3)(cid:373)(cid:258)(cid:410)(cid:286)(cid:396)(cid:349)(cid:258)(cid:367)(cid:3)(cid:373)(cid:258)(cid:455)(cid:3)(cid:271)(cid:286)(cid:3)(cid:393)(cid:396)(cid:381)(cid:410)(cid:286)(cid:272)(cid:410)(cid:286)(cid:282)(cid:3)(cid:271)(cid:455)(cid:3)(cid:18)(cid:381)(cid:393)(cid:455)(cid:396)(cid:349)(cid:336)(cid:346)(cid:410)(cid:3)(cid:367)(cid:258)(cid:449)(cid:3)(cid:894)(cid:100)(cid:349)(cid:410)(cid:367)(cid:286)(cid:3)(cid:1005)(cid:1011)(cid:3)(cid:104)(cid:856)(cid:94)(cid:856)(cid:3)(cid:18)(cid:381)(cid:282)(cid:286)(cid:895)(cid:3)
`This material may be protected by Copyright law (Title 17 U.S. Code)
`
`mchimica Acta, Vol. 40B, No. 4, pp. 6654379, 1985.
`cd in Great Britain.
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`0584—8547/85 $03.00+.00
`Pergamon Press Ltd.
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`Evaluation of the continuous optical discharge for spectrochemical
`analysis*
`
`DAVID A. CREMERS, FREDRICK L. ARCHULETA and RONALD J. MARTINEZ
`versity of California, Los Alamos National Laboratory, Chemistry Division, Los Alamos, NM 87545, U.S.A.
`
`(Received 25 June 1984; in revised form 6 September 1984)
`
`"u-act—-The continuous optical discharge (COD) has been studied as a spectrochemical excitation source for
`mic emission spectroscopy. The COD was generated by focusing a 45-W cw-CO2 laser beam in Xe gas at
`ssures between 1150 and 3200 torr. The high temperature (10000 K) and electron density (~ 10‘ 7 cm“ 3) of the
`should provide good excitation for elements difficult to excite by more conventional sources. Some
`d gas pressure. The design of a gas cell for
`iytical measurements which increases plasma stability is presented. Linear calibration curves for O2 and C12
`ioduced into the plasma were obtained and detection limits established. Detection limits were also determined for
`(1 materials laser ablated into the COD. Because the COD operates at pressures above atmospheric, gas samples
`most easily introduced for analysis. To prevent contamination of optical components by analyte dissociation
`ducts, the COD should be operated as a plasmatron.
`
`1.
`
`INTRODUCTION
`
`RRENTLY many different types of gas discharges are used to excite materials for analysis via
`o_mic emission spectroscopy. These discharges are produced by electric fields with a range
`frequencies: d.c. arcs (constant fields), a.c. arcs and sparks (1 kHz or less), the inductively
`upled plasma [ICP] (20-50 MHz) and microwave induced plasmas (~ 2.5 GHz). All of
`ese sources require some physical device to support the discharge: arcs and sparks require
`ectrodes, the ICP uses an induction coil, and microwave plasmas employ a resonator or
`veguide. Recently, however, it was hypothesized [1, 2] and then demonstrated that a free-
`nding continuous discharge can be produced by focusing the output of a sufficiently
`powerful cw-CO2 laser in inert [3—18] and molecular [19] gases and air [20, 21] at
`
`*Work performed under the auspices of the U.S. Department of Energy.
`
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