
Lazaros VarvarezosDublin City University | DCU · School of Physical Sciences
Lazaros Varvarezos
Doctor of Philosophy
SFI Postdoctoral Fellow in the School of Physical Sciences at DCU.
About
23
Publications
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Introduction
SFI Postdoctoral Fellow in the School of Physical Sciences at DCU. Current research interests include photoionization and dissociation of small quantum systems induced by X-ray free electron lasers, NIR table-top lasers and laser produced plasma sources in the soft X-ray spectral region. Developing a new femtosecond laser laboratory for ultrafast transient absorption spectroscopy and transient 2D-IR spectroscopy, in collaboration with chemistry at DCU.
Skills and Expertise
Education
January 2015 - January 2020
January 2014 - January 2015
January 2009 - January 2014
Publications
Publications (23)
Spatial and temporal characteristics of a table-top scale laser produced plasma formed on the surface of a tungsten target are reported. The emitted radiation was spectrally filtered to a narrow band of ca. 1 nm (FWHM) centred on a wavelength of 13.6 nm using a combination of Zr thin film transmission filters and a Mo-Si multilayer mirror (MLM). Th...
New information demonstrating the importance of both sequential and simultaneous (or direct) multiphoton ionization of inner shell electrons from neon is discussed in this paper. Ne was irradiated with intense 93 eV free electron laser (FEL) pulses at FLASH and studied with the aid of photoelectron spectrometry. This resulted in two and three photo...
It has been well established in the literature that surface contamination can adversely affect the aerodynamic performance of aerofoils and hence the efficiency with which turbines can convert wind to electrical power. Hence it is critical to ensure that turbine blades are kept as free as possible of contaminants. In this manuscript, we discuss LIB...
The photophysical properties of Cu(II) complexes with 5,10,15,20-meso-tetrakis(phenyl)porphyrin and 5,10,15,20-meso-tetrakis(N-methylpyridium-4-yl)porphyrin are examined via the luminescence and femtosecond time-resolved absorbance methods, respectively. These studies are supported by DFT and TD-DFT calculations, which highlight the important role...
The photophysical properties of Cu(II) complexes with 5,10,15,20-meso-tetrakis(phenyl)porphyrin and 5,10,15,20-meso-tetrakis(N-methylpyridium-4-yl)porphyrin were examined by luminescence and femtosecond time-resolved absorbance methods respectively. These studies were supported by DFT and TD-DFT calculations which highlight the important role playe...
An open-loop control scheme of molecular fragmentation based on transient molecular alignment combined with single-photon ionization induced by a short-wavelength free electron laser (FEL) is demonstrated for the acetylene cation. Photoelectron spectra are recorded, complementing the ion yield measurements, to demonstrate that such control is the c...
Steel impacts a variety of industries such as construction, automotive and ship building. The physical properties of steel (e.g., hardness, weldability) are significantly affected by the concentration of carbon. Hence, accurate determination of carbon content in steel has been, and still is, an active field of research. Laser induced breakdown spec...
We report on measurements of resonant three-step, two-colour ionization of atomic molybdenum, using a hollow cathode lamp (HCL) with optogalvanic detection. Wavelength scans were made for two specific transitions involved in the ionization pathways under investigation, namely 4d5(6S)5s 7S3 - 4d5(6S)5p 7P4 and 4d5(6S)5p 7P4 - 4d5(6S)6d 7D5.So-called...
The effect of laser wavelength on the dissociation mechanisms in methane is examined over a broad range of intensities for both 800 nm and 400 nm laser fields. It is found that, at lower laser intensities, the dissociation pathways identified with the aid of theoretical calculations for the methane cation can account for most of the experimental fi...
In this reply, we address the comments made by A N Ryabtsev on our paper (H Lu et al 2020 J. Phys. B: At. Mol. Opt. Phys. 53 115001). Specifically, we emphasize that the observed spectra depend critically on the plasma source type and conditions that pertain in the source. Our source of ions and experimental setup/method are quite different to the...
We report angle-resolved measurements on photoelectrons emitted upon near-threshold two-photon double ionization (TPDI) of Kr irradiated by free-electron laser (FEL) pulses. These photoelectron angular distributions (PADs) are compared with the results of semirelativistic R-matrix calculations. As reported by Augustin et al. [Phys. Rev. A 98, 03340...
In this work we investigate the effect of the confinement angle on self-colliding aluminium laser produced plasmas. More specifically, we apply V-shaped channel targets of different angles (90 • , 60 • and 30 •) and report both broadband and filtered time-resolved fast imaging measurements on the formation of such plasmas in ambient air. Based on t...
The photoabsorption spectrum of Bi + was measured in the wavelength range between 37 and 60 nm, using the dual laser plasma technique in which one plasma is used as the source of vacuum ultraviolet continuum radiation and the other plasma is used as the sample of atoms and/or ions to be probed. A number of features in the Bi + spectrum was identifi...
The photoabsorption spectrum of Bi + was measured in the wavelength range between 37 and 60 nm, using the dual laser plasma technique in which one plasma is used as the source of vacuum ultraviolet continuum radiation and the other plasma is used as the sample of atoms and/or ions to be probed. A number of features in the Bi + spectrum was identifi...
We have measured the photoabsorption spectra of Pb II and Bi III in the wavelength range between 37 and 70 nm. A number of features in the spectra have been identified with the aid of the Cowan suite of atomic codes. 5d → 6p transitions from the ground configuration (5d¹⁰6s²6p) and three excited configurations (5d¹⁰6s²6d, 5d¹⁰6s²7s, 5d¹⁰6s6p²) give...
We report oxygen K-shell photoabsorption measurements in CO2 plasmas, using a table-top laser produced plasma soft x-ray (SXR) and extreme ultraviolet source. Significant differences are observed between the photoabsorption spectra of the neutral CO2 molecule and photoionized CO2 plasmas, as new spectral features emerge in the case of the latter. T...
In this work we report soft x-ray (SXR) photoabsorption measurements in neutral methane and carbon dioxide molecules and their corresponding photoionized plasmas. The SXR radiation was generated by a table-top laser produced plasma source based on a double stream gas puff target. At low SXR intensities only features related to neutral molecules are...
Results of angle-resolved electron spectroscopy of near-threshold photoionization of Ne atoms by combined femtosecond extreme ultraviolet and near infrared fields are presented. The dressed-electron spectra show an energetic distribution into so-called sidebands, being separated by the photon energy of the dressing laser. Surprisingly, for the low...
In this work, we present measurements of the intensity-dependent photoelectron spectrum of Kr irradiated by the FLASH FEL tuned to a photon energy of 25.8 eV. Intensity dependent photoelectron spectra were obtained with the aid of a Velocity Map Imaging (VMI) spectrometer. As the FEL photon energy is close to threshold, two photon sequential double...
Results of angle-resolved electron spectroscopy of near-threshold photoionization of Ne atoms by combined femtosecond extreme ultraviolet and near infrared fields are presented. The dressed-electron spectra show an energetic distribution into so-called sidebands, being separated by the photon energy of the dressing laser. Surprisingly, for the low...