J. R. McNeil

Ultraviolet laser action from Cu II in the 2500‐Å region

We have obtained cw laser action from Cu II at 2486, 2506, 2591, and 2599 A by exciting a neon discharge in a copper hollow cathode. We have observed 7‐mW cw output power just above threshold and the output appears to saturate at 210 mW under quasi‐cw operation. The four ultraviolet laser lines observed originate from the 3d95s (3D) term of Cu II. The quantum efficiency of the 2500‐A laser transitions approaches 25%. Each of the four Cu II laser transitions has been employed in the past by spectroscopists as a secondary wavelength standard in the ultraviolet.

Discharge studies of the Ne‐Cu laser

Spontaneous‐emission and absorption studies of the Ne‐Cu hollow‐cathode laser are summarized. The major discharge processes operative in the Ne‐Cu laser are outlined and the qualitative aspects of a proposed model of the Ne‐Cu laser are discussed. Emphasis is placed on cathode sputtering as a source of copper atoms, and we demonstrate that copper densities of 1014 atoms/cm3 are created via discharge sputtering.

cw laser oscillation in Cu II

We have obtained cw laser oscillation on 23 transitions of Cu II in the blue‐green and near infrared by exciting either a He‐Ar, He‐Ne, or a He‐Xe discharge in a copper hollow cathode. The Cu II wavelengths range from 4506 to 7988 A. Output characteristics of the Cu II laser lines as functions of helium pressure; He:Ar, He:Ne, and He:Xe mixture ratios; and discharge current are presented. Single‐line output power, from the 7808‐A transition of Cu II, of 150 mW has been obtained.

Ultraviolet laser action in He‐Ag and Ne‐Ag mixtures

We report eight new laser transitions which span the wavelength region from 220 to 400 nm. Six of the ultraviolet transitions are observed in Ne‐Ag mixtures and two are observed in He‐Ag mixtures. The 227.8‐ and 224.3‐nm laser transitions of Ag II, 4d3D2‐5p3P01 and 4d1S0‐5p1P01 respectively, are the shortest‐wavelength cw laser transitions reported in the literature to date. Output characteristics of the ultraviolet laser transitions as a function of buffer gas pressure and discharge current are presented. The strongest laser transition 4d85s2 1G4→4d95p3F03, at 318.1 nm, provides single‐line peak output power of 350 mW. The output power does not appear to saturate at the limit of our input current, 50 A.

New ion laser transitions in He‐Au mixtures

We have observed 20 new laser transitions when exciting a helium discharge in a gold‐plated hollow cathode. The new ion laser transitions span the wavelength region from 253 to 763 nm. The behavior of laser power as a function of helium pressure and discharge current is presented. In general, the transitions have low threshold currents (<4 A), and the output power does not saturate at the limit of the discharge current. Multiline output power of 125 mW has been demonstrated in the 250–290‐nm region.

cw laser action in the blue‐green spectral region from Ag II

We have observed 18 cw laser transitions in Ne‐Ag mixtures spanning the wavelength region from 408.6 to 585.2 nm. The upper laser levels of Ag II are judged to be pumped by a charge‐transfer reaction between a ground‐state neon ion and a ground‐state Ag I atom resulting in simultaneous ionization and excitation of the silver atom. Output characteristics of the Ag II laser transitions as a function of neon pressure and discharge current are presented. The two strongest transitions are 478.8 and 502.7 nm in the blue and green, respectively.

Additional ultraviolet laser transitions in Cu II

We have observed three additional ultraviolet laser transitions in Cu II at 2529, 2600, and 2707 Å. To our knowledge, this is the first time these lines have been observed to oscillate.

Ultraviolet Ion Lasers

We have extended cw laser action down to 220 nm. This represents a 100 nm improvement to the state-of-the-art prior to our work. Moreover, we have obtained cw laser oscillation on twenty additional transitions in the spectral region between 220 and 320 nm.

Investigations of unidentified laser transitions in Ag II

We originally reported 33 laser transitions in He‐Ag and Ne‐Ag mixtures, 23 of which were reported as unidentified. We have since made a more thorough investigation of the laser output and have positively identified five of the unidentified laser transitions as Lyman ghosts. The remainder of the unidentified laser transitions are also believed to be spectrometer ghosts.

Temperature of neutral copper and neon atoms in a hollow cathode laser discharge

Abstract From measurements with a Fabry-Perot interferometer it was found that neon and copper neutrals in the active part of a hollow cathode charge transfer laser discharge have kinetic temperatures of 1000 K and 2100 K, respectively.