M. A. Kalyar

Spectroscopic characterization of laser ablation brass plasma

We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated.

Absolute photoionization cross section from the 6s6p 1,3P1 excited states of barium

We present photoionization cross section measurements from the 6s6p 1 P1 and 3 P1 excited states of barium at and above the first ionization threshold. The experiments have been performed using a thermionic diode ion detector in a space charge limited mode in conjunction with a Nd:YAG laser system and the saturation technique to determine the photoionization cross sections. The absolute values of the photoionization cross section from the 6s6p 1 P1 and 3 P1 excited states at the first ionization threshold have been determined as 90 ± 14 Mb and 102 ± 15 Mb, respectively. The measured values of the photoionization cross section from the 6s6p 1 P1 excited state are compared with available experimental and theoretical work, while the absolute photoionization cross sections from the 6s6p 3 P1 excited state are reported for the first time. (Some figures in this article are in colour only in the electronic version)

Photoexcitation study of the 4s 2 S 1/2 state of atomic sodium

We report the first measurements of oscillator strengths for 4s 2 S1/2 → np 2 P1/2,3/2 (19 n 57) Rydberg transitions in atomic sodium using a thermionic diode ion detector in conjunction with an Nd:YAG pumped dye laser system. The f-values have been calibrated with the measured photoionization cross-section from the 4s 2 S1/2 excited state at the first ionization threshold as 0.65(0.10) Mb. The binding energy of the 4s 2 S1/2 level is determined as 15 709.444(8) cm −1 by employing the Rydberg relation to the observed np 2 P1/2,3/2 Rydberg series. Addition of the binding energy to the known energy of the 4s 2 S1/2 level yields the first ionization potential of sodium as 41 449.44(1) cm −1 , which is in excellent agreement with the recognized value. (Some figures in this article are in colour only in the electronic version)

Experimental studies of the oscillator strengths of the 6s6p 1,3P1 → 6snd 1,3D2 Rydberg transitions in barium

We report new measurements for the oscillator strengths of the 6s6p 1P1 → 6snd 1D2 and 6s6p 3P1 → 6snd 3D2 Rydberg transitions of barium using a thermionic diode ion detector in conjunction with a Nd:YAG pumped dye laser system. The f-values have been calibrated with the absolute photoionization cross-section measured at the first ionization threshold from the 6s6p 1P1 and 6s6p 3P1 excited states employing the saturation technique. An excellent agreement is found for the 6s6p 1P1 → 6snd 1D2 Rydberg transitions with the earlier reported work. The data on the oscillator strength of the 6s6p 3P1 → 6snd 3D2 Rydberg transitions are reported for the first time. The oscillator strength densities in the continuum corresponding to the 6s6p 3P1 excited state have also been determined and a smooth merging of the discrete f-values into the oscillator strength densities is observed across the ionization threshold.

Multi-photon excitation spectra of the 3snℓ (ℓ = 0, 1, 2 and 3) Rydberg states of magnesium

New experimental data on the highly excited l = 0, 1, 2 and 3 Rydberg states of magnesium have been acquired using two-photon and two-step laser excitation technique in conjunction with a thermionic diode ion detector. The new observations include even parity 3sns 1S0 (8 ≤ n ≤ 24) and 3snd 1D2 (7 ≤ n ≤ 62) Rydberg states approached directly from the 3s2 1S0 ground state via two-photon excitation, and the odd parity 3snp 1P1 (20 ≤ n ≤ 61) and 3snf 1F3 (14 ≤ n ≤ 66) Rydberg states accessed by the two-step excitation process via 3s4s 1S0 and 3s3d 1D2 intermediate states. The Rydberg relation fit to the new data of the np 1P1 and nf 1F3 series yields the binding energies of the 3s4s 1S0 and 3s3d 1D2 levels as 18 167.702 cm−1 and 15 267.972 cm−1, respectively. By adding the binding energies to the corresponding energies of the aforementioned levels, a precise value of the first ionization potential of magnesium is determined as 61 671.04 ± 0.04 cm−1. Using this ionization potential value, the quantum defects for the ns 1S0, np 1P1, nd 1D2 and nf 1F3 Rydberg series have been determined as 1.526(2), 1.046(2), 0.602(2) and 0.049(2) cm−1 respectively.