First Spectrum of Tungsten

Abid Husain, S. Jabeen, Abdul Wajid
2018 Journal of Atomic Molecular Condensate and Nano Physics  
The spectroscopic data of tungsten (W) is important for plasma science, as it is used as a diverter and in ITER. We have recorded the spectrum of tungsten on a 1.5-m Wadsworth spectrograph in the 2100-4900 Å wavelength range. The ground configuration of the neutral tungsten is 5d 4 6s 2 . First excited configurations in the odd parity system are 5d 3 6s 2 (6p + 7p + 5f + 6f) + 5d 4 6s6p. The 5d 4 6s6p configuration has already been studied. We have identified hundreds of lines in this spectrum
more » ... nd confirmed fifty nine levels of the 5d 4 6s6p configuration. Relativistic Hartree-Fock (HFR) and least squares fitted (LSF) parametric calculations were carried out to interpret the observed spectrum. We have found good agreement with the previously published data. First Spectrum of Tungsten: A. Husain et al. reported ten new even energy level, of which 161 lines were previously unclassified. Kramida and Shirai in 2006 [5] reported the compilation of wavelengths, energy levels, and transition probabilities for Jean-Francois Wyart [6] in 2010 reported two new levels, one belonging to J = 0 and another belonging to J = 3, with LS percentage compositions. However the assigned configurations were a mixing of 5d 4 6s6p, 5d 3 6s 2 6p, 5d 5 6p. Experimental Details The spectrograph was equipped with a grating of 1200 lines/mm surface density and giving a linear inverse dispersion of 5.45 Å/mm for the first order wavelength [7] . Pure tungsten metal wire was used to make two electrodes of appropriate sizes in order to fix them in the gap of electrode chamber. The electrodes are moved across the slit until maximum intensity is observed at the center of the slit. Both the electrode were then connected to capacitors of 2.5 µf charged through high voltage power supply up to 1.5 KV to 2 KV. The tungsten atoms are then excited due to a spark discharge between electrodes. After loading the plate, numbers of exposures were taken with different exposure times so as to obtain optimized line intensities on the spectrum. Recording of the spectrum were performed with 187 shot (numbers of sparks). The tungsten spectrum was recorded on the photographic film as well as paper and Mercury lines were recorded on the same plate keeping the exposure time 35 seconds. These lines of known wavelengths were used as the standard in MOSFIT program for the calibration of tungsten. Results and Discussion The ab-initio calculation were performed using Cowan's computer code [8] incorporating the configuration 5d 4 6s 2 , d 5 6s,and d 4 6s7s for even parity matrix and 5d 4 6s6p, 5d 3 6s 2 6p and 5d 5 6p configurations for odd party matrix. The initial energy parameter scaling applied for E av and ζ at 100% of the HFR values and F k at 85%, G k and R k at 75%of the HFR values. The reported values of levels were taken from NIST ASD [9] levels list. The levels were used to run least square fitted (LSF). This allowed adjusting of the energy to the real values and hence a better prediction was achieved. All the previously reported even parity energy levels, three level of j = 0, three levels of j = 1, eight level of j = 2, six levels of j = 3, six level of j = 4, two levels of j = 5 and two levels of j = 6 with configuration 5d 4 6s 2 have been obtained. Most of the energy levels fitted excellently, however some of the levels showed larger deviation. It was observed that it is due to strong mixing of other configurations 5d 5 6s and 5d 4 6s7s with 5d 4 6s 2 . Of all the odd parity energy levels reported earlier, sixteen levels of j = 0, forty four levels of j = 1, seventy one levels of j = 2, seventy one levels of j = 3, sixty eight level of j = 4, fifty levels of j = 5, thirty levels of j = 6 and ten levels of j = 7 belonging to configurations 5d 4 6s6p, 5d 3 6s 2 6p, 5d 5 6p have been obtained. In our recording between the wavelengths 2100-4900 Å many unclassified lines were observed. One hundred and two transition belonging 5d 4 6s 2 and 5d 4 6s6p which have been observed in our spectrum are shown in Table 1 . The energy parameters for even parity levels and LSF are given in Table 2 and 3, respectively. The energy parameters for odd parity levels and LSF are given in Table 4 and 5, respectively.
doi:10.26713/jamcnp.v5i2.753 fatcat:dkjjutvqqbhznfvinrqvt42xga