Interatomic Potentials of Cd - He from Far-Wing Line Shapes

Abstract

The intercombination absorption line of the Cd (326.1 nm) line broadened by pressure effects of He in the spectral range extending from 1400 cm-1 in the blue wing to 2000 cm-1 in the red wing was studied using a high resolution spectrometer. The temperature dependence of the studied line was analyzed in the framework of the quasi-static theory. This analysis allowed us to determine the ground (X10+), and the excited (31, 30+) state potentials at internuclear separations from 3.3 Å to 5.5 Å. The well depths with their positions for these states are respectively equal to (16.3 ± 2 cm-1, 4.5 ± 0.2 Å), (2.55 cm-1, 4.94 ± 0.3 Å) and (45.8 ± 3 cm-1, 3.8 Å). These values are in close agreement with those obtained for this mixture (Cd - He) from other experimental methods. The van der Waals coefficient differences between the ground 10+ state and the two exited states 30+ and 31 (ΔC60 and ΔC61) are obtained from the near red wing profile using Kuhn's law. The values of ΔC60 and ΔC61 are found to be equal to 14.8 ± 2 and 28.5 ± 3 eV Å6 respectively.

The intercombination Cd line 326.1nm and van der Waals potential coefficients for pure Cd and Cd–inert gas systems

“…Generally for Cd-rare gases such a linear dependence of the log K m n ðDmÞ is observed in two regions of the near red wing profile [2][3][4][5][6][7]:…”

“…It is a straight line whose slope is equal to (À1.5). In this region Kuhn's law (3) holds and the van der Waals' coefficient difference DC 1 6 can be determined. Taking the theoretical value of the oscillator strength of the investigated line as equal to 1.6 Â 10 À3 [17], the van der Waals' coefficient difference DC 1 6 is found to be 168.8 ± 2 eV Å 6 .…”

“…In the vicinity of this band two linear regions with slope (À3/2) are observed for the (Cd-inert gases) system. The first one close to the line center may be interpreted as the quasi-static line wing which is formed by transitions between the ground state 1 0 + and excited states 3 0 + as well as 3 1, while the second corresponds to the transition to the excited 3 0 + state only as was mentioned in the theoretical part and established in [2][3][4][5][6][7]. The van der Waals coefficients DC 0 6 and DC 1 6 originating due to these states are presented in Table 1.…”

“…Recently, there have been numerous spectroscopic determinations of interatomic potentials of the ground and excited states of these systems [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

Broadening and shift of the inter-combination spectral line of Cd 326.1 nm perturbed by Kr

“…During the past several decades, there have been numerous investigations of vdW molecules, especially for pure cadmium and cadmium inert gas systems [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. There are some papers reporting experimental and theoretical studies [10][11][12][13][14][15][16][17][18][19][20] that have been performed for obtaining the interatomic potentials for Cd + Kr using the Cd inter-combination spectral line at 326.1 nm (5 3 P 1 → 5 1 S 0 ).…”