Influence of spectral line broadening on the mode structure of He-Kr and He-Ar gas lasers

Abstract

Using the semiclassical perturbation approach, Stark broadening parameters for Kr II 469.4 nm, Ar II 476.5 nm, and Ar II 480.6 nm spectral lines have been determined. The obtained results have been used for the investigation of the role of the Stark broadening mechanism on the mode properties of hollow cathode excited noble gas mixture lasers. It has been found that for the He-KrII 469.4 nm laser broadening by neutral atom collisions is large enough to explain the single-mode operation of this laser, as opposed to the He-ArII 476.5 nm laser where Stark broadening also has to be taken into account to explain this property.Introduction. In this work, the full semiclassical perturbation approach [1, 2] has been applied for the determination of Stark broadening parameters of Kr II 469.4 nm, Ar II 476.5 nm, and Ar II 480.6 nm lines and a joint laser physical application of the results obtained; namely the role of Stark broadening on the mode properties of hollow cathode excited noble gas mixture lasers is discussed.Stark Broadening Parameters Calculation. All details of the semiclassical perturbation approach [1, 2] used here for the Stark broadening parameter calculations are given in [3] and a comparison of the obtained results with existing experimental and theoretical calculations (see [4] and references therein) will be presented elsewhere. We note only that we checked the influence of the missing Kr II 7p levels and found it to be not important. The determined Stark broadening parameters for the Kr II 469.4 nm, Ar II 476.5 nm, and Ar II 480.6 nm lines are shown in Tables 1 and 2.Stark Broadening in Hollow Cathode Laser Discharges. Ionic lines can be effectively excited in a hollow cathode (HC) discharge due to the presence of high-energy electrons. It has been used since 1970 for the excitation of a lot of noble gas-metal vapor and noble gas mixture ion lasers [5].An interesting feature of the HC lasers is that they oscillate usually in a single axial mode without any optical selection. This property has been attributed to the large homogeneous line-width due to the relatively large filling pressures. Recent studies have shown, however, that, in several cases, broadening by collisions with neutral atoms is not large enough to explain single-mode operation [6], and Stark broadening has also to be taken into account [7]. Therefore it seemed to be reasonable to study the role of the Stark effect at the He-Kr + 469.4 nm and He-Ar + 476.5 nm HC lasers [8,9].The HC laser discharge. For laser purposes the discharge inside the cathode is used for the excitation. Different HC geometries are applied, most frequently "longitudinal" or "transversal" systems [10]. The typical pressure in the tube is 10-25 mbar. In a HC discharge the electron energy distribution function has generally a nearly Maxwellian low-energy part with a high-energy tail. The mean energy of the low-energy part amounts to E e = 0.1-1.0 eV, while the high-energy tail can rise up to the cathode voltage, which is commonly several hundred V. For laser exc...

Semiclassical perturbation Stark widths of singly charged argon spectral lines

“…In Fig. 4, we present the temperature dependence of Ar II Stark widths due to collisions with positive ions (Ar + ) for an electron density of 10 17 cm −3 for three spectral lines: Dimitrijević & Truong-Bach (1986) and Dimitrijević & Csillag (2006) (W D ). W e is calculated with the SCP approach (Sahal-Bréchot 1969a,b) and a set of atomic data determined using the Cowan code (Cowan 1981).…”

“…The energy levels were taken from Bashkin & Stoner (1975) and oscillator strengths were calculated using a scaled Thomas-Fermi model (Stewart & Rotenberg 1965). Dimitrijević & Csillag (2006) performed SCP calculations of the Stark width for two multiplets (476.5 and 480.6 nm) using energy levels from Bashkin & Stoner (1975) and oscillator strengths calculated using the Bates & Damgaard method. A sophisticated SCP calculation of Stark broadening parameters for a large number of spectral lines of Ar II would be useful in improving the investigation of this broadening mechanism.…”

Division Xii / Commission 14 / Working Group Collision Processes

“…Ar ii 476.5 nm, 480.6 nm and Kr ii 469.4 nm lines (Dimitrijević & Csillag 2006), Cd i 33 singlets and 37 triplets (Simić et al 2005a), 26 Ne v multiplets (Hamdi et al 2007) and 15 Si VI multiplets (Hamdi et al 2008). Djurović et al (2006) have presented a review of experimental work on Stark broadening of 80 singly ionized xenon lines and Purić et al (2008) have used published Stark widths for spectral lines originating from 3s-3p transition arrays of multiply charged ions, to establish trends from which Stark widths are predicted for Mg vii, Mg ix, Mg x, Na vii, Na viii, Al viii, Al ix, Si xi, Ti xi, Cr xiii, Cr xiv, Fe xv, Fe xvi, Fe xxiii and Ni xviii.…”

“…For isolated lines, Stark broadening is dominated by collisions with plasma electrons. Broadening parameters have been determined theoretically for: Ar ii 476.5 nm, 480.6 nm and Kr ii 469.4 nm lines (Dimitrijević & Csillag 2006), Cd i 33 singlets and 37 triplets (Simić et al 2005a), 26 Ne v multiplets (Hamdi et al 2007) and 15 Si VI multiplets (Hamdi et al 2008). Broadening parameters have been obtained experimentally for: C i 247.8561 nm (Djeniže et al 2006b), Mg ii 448.1 nm (Djeniže et al 2005b), Fe i 381.58 nm (Bengoechea et al 2006) and Fe i 538.34 nm (Bengoechea et al 2005) Stehlé et al (2005) have examined current Stark broadening theory as a basis for diagnostics of low-temperature plasmas and Mahmoudi et al (2008) have provided new expressions for diagonal multiplet factors of complex configurations, required for studies of isolated lines.…”

On the semiclassical perturbation Stark shifts of Ar II spectral lines

“…Alonso-Medina & Colón (2007) used Ar II spectral lines for the determination of temperature and electron density of laser induced lead plasma. Beside laboratory plasmas, singly charged argon spectral lines are also of interest for argon laser (Dimitrijević & Csillag, 2006). Ar II spectral lines are also observed in stellar atmospheres.…”