Sohail MushtaqMass Spectrometry Instruments Limited · Research & Development
Sohail Mushtaq
PhD
About
25
Publications
5,493
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252
Citations
Citations since 2017
Introduction
Current working project.
1) Choas in real mass spectral data: The analysis of non-conducting samples in powder form using dc source.
Technique: GD-MS
2) Qualitative and quantitative elemental analysis of molybdenum inorganic compounds and complexes in form of solid flakes. Instrument: GD90 Trace GD-MS
3) Ultra-(trace) elemental analysis of low melting point materials using GD90 Trace GD-MS
Additional affiliations
January 2019 - July 2021
MASS SPECTROMETRY INSTRUMENTS LIMITED
Position
- Researcher
March 2017 - June 2018
September 2011 - February 2017
Education
February 2008 - July 2011
Publications
Publications (25)
In argon glow discharge (GD) plasma, ionization processes for chlorine are independent of metastable states and ions of the plasma gas due to its higher ionization energy as compared to Arm and non-availability of suitable ionic energy levels for selective state population. Electron ionization is the only way of producing singly charged ions of chl...
This tutorial review covers the terms scheme, energy levels, and populating/depopulating processes for the atomic metastable states of sputtered and analytically interesting atoms.
The partial periodic table shows elements, with colored background, which have been reported for charge transfer excitation (CT) reactions in glow discharges (data from 1987–2019). Recently, a CT reaction b/w Mo atoms & Ar ⁺ has been identified.
Charge transfer excitation processes in analytical glow discharges are important species and state selective processes that can have a considerable effect on the intensities of lines in the associated optical emission spectra and the total populations of ions in the associated mass spectra. These charge transfer excitation processes have been the s...
We report a combined experimental/modelling study of optical emission from the A2Δ, B2Σ− and C2Σ+ states of the CH radical in microwave (MW) activated CH4/H2 gas mixtures operating under a range of conditions relevant to the chemical vapour deposition of diamond. The experiment involves spatially and wavelength resolved imaging of the CH(C->X), CH(...
Microwave (MW) activated H2/Ar (and H2/Kr) plasmas operating under powers and pressures relevant to diamond chemical vapor deposition have been investigated experimentally and by 2-D modeling. The experiments return spatially and wavelength resolved optical emission spectra of electronically excited H2 molecules and H and Ar(/Kr) atoms for a range...
A microwave (MW) activated hydrogen plasma operating under conditions relevant to contemporary diamond chemical vapour deposition reactors has been investigated using a combination of experiment and self-consistent 2-D modeling. The experimental study returns spatially and wavelength resolved optical emission spectra of the d→a (Fulcher), G→B and e...
Diamond synthesis by chemical vapour deposition (CVD) from carbon-containing gas mixtures has by now long been an industrial reality, but commercial interest and investment into the technology has grown dramatically in the last several years. This Feature Article surveys recent advances in our understanding of the gas-phase chemistry of microwave-a...
Normally, in analytical GD-MS, the doubly charged metallic ion signals from the sample are several orders of magnitude less than the corresponding singly charged signals. However, we have observed that using a neon plasma, the M++ signals of some elements, which have double ionization energies close to the first ionization energy of neon, are of th...
Extensive investigations have been carried out in recent years on the effects of the presence of small
amounts of molecular gases in analytical glow discharges (GDs) using argon as the plasma gas.
Complementary studies using neon have shown that, when hydrogen is added to a neon discharge with
a copper sample, the intensities of lines from most of...
The excitation of Cu+ ions in a Ne glow discharge with small additions of H2, O2 and N2 was studied. Ratios of radiative transition rates between different Cu II levels in a discharge in neon, with and without the molecular gas added, were calculated, and the formalism of transition rate ratio (TRR) diagrams was developed and used to study the chan...
We report TOFMS investigations on the effects of hydrogen added to a dc GD argon plasma, in detail over the most likely concentration range occurring in analytical work (0 - 0.10% v/v), together with an overview to 0.8% v/v; typical GD-OES discharge condition were used. Many previous studies on the effects of hydrogen in analytical GD-MS used much...
Analytical Glow Discharge (GD) Optical Emission Spectroscopy and GD Mass Spectrometry have important industrial applications. The analytical accuracy may be affected by trace molecular gases. High resolution FTS is used to investigate fundamental discharge processes.
Transition rate diagrams of copper ions in argon and neon glow discharges are presented using data from Cu II emission spectra. Based on the transition rate diagrams, several different collisional processes between ground state and metastable atoms and ions of copper and the discharge gas are proposed as probably significant for populating upper le...
The emission spectra of iron observed using a Grimm-type glow discharge in argon, argon with 0.3% v/v hydrogen and neon were studied to identify major excitation and ionization processes of iron ions in the plasma. Transition rate diagrams are given for iron ions in those discharges. These are particularly useful for describing situations in which...
Many studies have already been carried out on the effect of small quantities of molecular gases (oxygen, hydrogen and nitrogen) in argon analytical glow discharges (GD). We report here the first comprehensive study using small amounts of oxygen in a neon GD plasma with copper sample. Whilst neon is too costly for routine use in analytical GD spectr...
In many cases in both argon and neon plasmas, there is enhanced excitation of analyte atomic lines with upper energies close to 5 eV in the presence of small amounts of hydrogen or oxygen. To observe this effect fully, it is essential to record spectra over a very wide spectral range, so as to include as many energy levels as possible, otherwise cr...
The emission spectra of manganese observed using a Grimm-type glow discharge in pure argon, argon with 0.3% v/v hydrogen and pure neon were studied in order to identify major excitation and ionization processes of manganese in the plasma. A new procedure is proposed, in which each observed emission line is associated with the corresponding transiti...
The increasing use of mixed gases, including helium mixtures, in glow discharge mass spectrometry has led to a need to understand the resulting signal enhancements due to changes in excitation and ionization processes. To understand more fully these processes in glow discharge, we have carried out complementary optical emission spectrometry experim...
The presence of oxygen has significant effects in a mixed argon–oxygen glow discharge plasma. Previous studies of these effects did not use added oxygen in concentrations that would be expected in typical analytical oxide samples in glow discharge. We report results of studies using glow discharge optical emission spectrometry (GD-OES) to investiga...
In low pressure glow discharges such as the Grimm-type source, the relative intensities of lines in the analyte spectrum depend primarily on the plasma gas. The probability of selective excitation of certain analyte spectral lines by asymmetric charge transfer (ACT) involving carrier gas ions is increased if excited levels are close to resonance. T...
The influence of up to 0.8 % O2 on the Ar plasma in a dc analytical glow discharge was studied on Fe, Ti, Cu and Au samples using time of flight mass spectrometry and high resolution optical Fourier transform spectrometry. All positive ion signals decreased gradually by 2 to 3 orders of magnitude with increasing O2. In addition, a sudden 100-fold d...
We report results of studies using Fourier Transform Optical Emission Spectroscopy (FT-OES) to investigate the effects of added oxygen (0.04–0.8% v/v) on observed spectra from a Grimm-type glow discharge, generated in argon plasma with a pure iron sample. Significant changes in the sputter rate and the intensities of atomic lines of the carrier gas...
The hollow cathode discharge was investigated and compared with the plane cathode discharge in a Grimm-type source studying a large number of lines with iron and titanium as cathode materials in argon plasma. The high resolution Fourier Transform Spectrometer (FTS) at Imperial College (IC) was used for recording spectra. The intensity changes for a...
Questions
Questions (3)
I am interested to understand the collisional process between hydrogen molecular ions with analyte atoms in low pressure glow discharge plasmas. Any relevant data and information regarding the published papers would be appreciated.
In analytical glow discharge plasma with 700 V, 20 mA, there is massive increase in doubly charged argon ion, Ar++, (about 3 orders of magnitude) with the increase of small amount of hydrogen in argon plasma. Any possible explanation of this increase? On the other hand, as well established thing now, there is pronounced decrease in the argon ion population (Ar+) with the increase of hydrogen.
