A "reference cell" for generating radio-frequency (rf) glow discharges in gases at a frequency of 13.56 MHz is described. The reference cell provides an experimental platform for comparing plasma measurements carried out in a common reactor geometry by different experimental groups, thereby enhancing the transfer of knowledge and insight gained in rf discharge studies. The results of performing ostensibly identical measurements on six of these cells in five different laboratories are analyzed and discussed. Measurements were made of plasma voltage and current characteristics for discharges in pure argon at specified values of applied voltages, gas pressures, and gas flow rates. Data are presented on relevant electrical quantities derived from Fourier analysis of the voltage and current wave forms. Amplitudes, phase shifts, self-bias voltages, and power dissipation were measured. Each of the cells was characterized in terms of its measured internal reactive components. Comparing results from different cells provides an indication of the degree of precision needed to define the electrical configuration and operating parameters in order to achieve identical performance at various laboratories. The results show, for example, that the external circuit, including the reactive components of the rf power source, can significantly influence the discharge. Results obtained in reference cells with identical rf power sources demonstrate that considerable progress has been made in developing a phenomenological understanding of the conditions needed to obtain reproducible discharge conditions in independent reference cells.

Laser action at 1315nm on the I(P1∕22)→I(P3∕22) transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O2(a1Δ) which is produced using wet-solution chemistry. The difficulties in chemically producing O2(a1Δ) has motivated investigations into purely gas phase methods to produce O2(a1Δ) using low-pressure electric discharges. In this letter, we report on the demonstration of a continuous-wave laser on the 1315nm transition of atomic iodine where the O2(a1Δ) used to pump the iodine was produced by a radio-frequency-excited electric discharge. The electric discharge was sustained in a He∕O2 gas mixture upstream of a supersonic cavity which is employed to lower the temperature of the continuous gas flow and shift the equilibrium of atomic iodine in favor of the I(P1∕22) state. The laser output power was 220mW in a stable cavity composed of two 99.99% reflective mirrors.

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Laser action at 1315 nm on the I͑ 2 P 1/2 ͒ → I͑ 2 P 3/2 ͒ transition of atomic iodine is conventionally obtained by a near-resonant energy transfer from O 2 ͑a 1 ⌬͒, which is produced using wet-solution chemistry. The system difficulties of chemically producing O 2 ͑a 1 ⌬͒ has motivated investigations into gas phase methods to produce O 2 ͑a 1 ⌬͒ using low-pressure electric discharges. In this letter we report on positive gain on the 1315 nm transition of atomic iodine where the O 2 ͑a 1 ⌬͒ was produced in a flowing electric discharge. The electric discharge was followed by a continuously flowing supersonic cavity that was necessary to lower the temperature of the flow and shift the equilibrium of atomic iodine more in favor of the I͑ 2 P 1/2 ͒ state. A tunable diode laser system capable of scanning the entire line shape of the (3,4) hyperfine transition of iodine provided the measurements of gain.

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