Shang Yi Ch'en

Thermodynamic Conditions of the Test Gas in a Ballistic Compressor

The development of a free‐piston compressor at the University of Oregon is described. In order to characterize the thermodynamic conditions of the test gas in the ballistic compressor, a theoretical analysis of the pistons motion is made taking into account gas leakage, viscous friction, and heat losses. The values used for the radial clearance of the piston and the heat‐loss constant are chosen so that the computed peak pressure and minimum volume of the test gas agree with experiment. The predictions of this treatment are then compared with observed pressure and acceleration profiles which were taken using argon and helium as test gases over a range of peak test‐gas pressures from 476 to 1660 atm and are found to be in good agreement. The acceleration profile is found to be more sensitive than the pressure profile. It is evident that the compression process is nonadiabatic due to gas leakage around the piston and heat losses to the compressor walls.

Pressure shift and broadening of the resonance lines of singly ionized alkaline-earth atoms and some alkali atoms in hot compressed Ar and He

Abstract With a ballistic compressor, the pressure shift and broadening of the resonance lines of singly ionized Ca, Sr and Ba were measured under various pressures of Ar and He at 2400 and 2500°K respectively. To make a comparison with the corresponding effects for alkali atoms, the first member of the principal series and that of the diffuse series of neutral Li and Na-D lines were also studied under the same experimental conditions. By tabulating the results of this paper and previous articles on neutral alkaline-earth resonance lines, it is found that the shift and broadening of the resonance lines of atoms belonging to the three different groups are quite alike. The amounts of shift and broadening taper off slightly in the order of neutral Group (IA), neutral Group (IIA) and singly-ionized Group (IIA) atoms in the periodic table.

Interpretation of measured spectral line shapes using a square-well potential: The absorption lines of cesium broadened by rare gases

Abstract A simple square-well potential is used as an aid in understanding the complicated evolution of the absorption lines and their associated satellites for cesium perturbed by the rare gases. New experimental halfwidth data for cesium perturved by Xe, Ar, and He are presented. In the case of Xe, data for the second, third and fourth members are presented to 30, 7, 1 rd (relative density), respectively. For Ar, data are presented for the third through the ninth member. The pressure range for the third and fourth members is from 0 to 20 rd. For the other members, it ranges to 8 rd for the fifth and to 2 rd for the ninth. Third and fourth member helium data are presented to about 20 and 8 rd, respectively. Several theoretical computer profiles are used to illustrate the evolution of the line and satellites with foreign gas pressure and these are compared with the experimental data.

The shift of iron emission lines produced by argon and helium

Abstract The shifts of all the strong emission lines of the neutral iron atom in hot compressed argon and helium (produced by a ballistic compressor) were measured in the region 2497–5900 A. Curves showing the shift vs. relative density (r.d.) are presented for 68 of these lines with argom and 14 with helium, over a range of r.d. from 28 to 104 at 3230°K for argon and from 36 to 108 at 3600°K for helium. For argon, the relative displacements of various spectral terms of FeI with different J, L, S or electron configurations are discussed. A decrease in red shift was observed at higher temperatures.

The shift of the emission lines of Cr and Ni produced by argon and helium

Abstract The shifts of all strong emission lines of neutral Cr and Ni in the wavelenght ranges of 3014–5328 A, and 3050–3619 A, respectively, with argon and of 3017–4651 A and 3369–3619 A, respectively, with helium have been measured. The temperatures and the relative densities (r.d.) of the gases at which observations were made are, respectively, 3230°K and 28–104 for Ar and 3600°K and 60–108 for He. The shift vs. r.d. relationship for 14 CrI lines and 11 NiI lines with argon, and 12 Cr lines and a single Ni line with helium, are tabulated. Some lines show a linear dependence of shift on r.d. and some behave linearly for low r.d. but quadratically for higher r.d. The general statements about the behavior of the relative shifts of spectral levels with respect to L and S values are the same as those for the FeI lines. The normal fine-structure levels (many multiplets of CrI) behave in their relative shifts oppositely to those of inverted levels (FeI), although the behavior depends on the more detailed structure of the levels.

Intensity analysis of the nature of Rb/Xe red satellite bands☆

Abstract Absorption intensities of the doublet lines, and their associated red satellite red satellite bands, for the first three members of the xenon perturbed rubidium principal series were analyzed in order to investigate the nature of the bands. From the intensity variation with xenon pressure, it is concluded that the bands are not due to molecular formation in the Rb electronic ground states. The ideas of molecule formation in the Rb electronic excited states were only partially confirmed. In transitions from the atomic states 2 P 3 2 and 2 P 1 2 to other states of quantization, the interatomic potential at small distances seems to be more complicated than the one customarily used in qualitative discussions on the production of bands.

Pressure broadening and shift of the first diffuse series doublet of indium due to the presence of helium and argon

Abstract The shift and half-width of In λ 3039 and In λ3256 was measured in Ar and He under pressures up to one thousand p.s.i. The temperature of the absorption tube was 850°C for In λ 3039 and 930°C for In λ 3256. The van der Waals interaction constant for In/Ar was found to be 1·5 x 10 -30 and 8·6 x 10 -31 cm 6 /sec for In λ 3039/Ar and In λ 3256/Ar respectively. In λ 3256 exhibited a small red shift in He for the range of r.d. (from 1 to 16) of He employed.

Pressure effects of argon and helium on the first diffuse series doublet of singly ionized barium

Abstract The shift and broadening of the first diffuse series doublet of Ba II in emission was observed under various relative densities of Ar (20–107) and He (35–121) at 2500°K. By comparing the present data with those of the shift of the principal series doublet from a previous paper, it is suggested that argon pressure causes a downward displacement for 6p2P and 6d2D levels and an upward one for 5d2D and 7s2S levels, with respect to the ground state of Ba II.

The shift and broadening of the resonance lines of Ca, Sr and Ba in hot, dense argon and helium☆

Abstract The shift and half-width of the resonance singlet lines of Ca, Sr and Ba in emission were measured under various relative densities between 20 and 70 for Ar (at 2500 K) and between 35 and 121 for He (at 2450 K) by means of a ballistic compressor. The shift due to Ar is always red and increased with increasing relative density. The shift due to He is slightly toward red at densities below 50 and then gradually turns to the violet as the relative density is further increased. The foreign gas shift and broadening is nearly the same for the resonance lines of all these different alkaline-earth atoms but is different for different foreign gases, as in the case of alkali metals. Comparison with previous observations of Ca at 910 K shows that the increase of temperature will cause a decrease in red shifts and half-widths.

The shift of some strong lines of Al, Ca, Cu, Mn, Mo, and Na in emission, produced by argon☆

Abstract The shift of the resonance lines of Ca, Cu, Mn, and Na and of AlI λ3082 and λ3944, CaII λ3933 and λ3968, and MoI λ3358 was measured in emission when perturbed by hot, dense argon at 3239°K (r.d. 35–100) in a ballistic compressor. Some of the results are compared with those previously obtained with static argon pressures.