M. Allegrini

University of Pisa, Physics, Faculty Member

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Nesreen ghaddar

American University of Beirut

Soteris Kalogirou

Cyprus University of Technology

naveen noronha

Visvesvaraya Technological University

Praveen Surolia

Manipal University Jaipur

Iain Staffell

Imperial College London

Farzad Jafarkazemi

Islamic Azad University, South Tehran Branch

Kiran Dasari

University of Illinois at Urbana-Champaign

Professor Bashir O M O L A R A N Bello

University of Abuja, Nigeria

A. Z. Hafez

University of Nottingham

Foo Wah Low

Universiti Tunku Abdul Rahman

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Papers by M. Allegrini

Energy transfer collisions in laser excited mixtures of alkali vapors

AIP Conference Proceedings, 1989

Energy transfer collisions between two laser excited alkali atoms of different species have been ... more Energy transfer collisions between two laser excited alkali atoms of different species have been investigated in cell experiments using an intermodulation technique. Cross sections have been measured for the potassium/rubidium mixture and evidence of three-body collisions in presence of a buffer gas has been obtained in the sodium/potassium mixture.

Experimental method for measuring electronic energy transfer cross sections in laser-excited atomic vapors

Domain pattern formation and kinetics on ferroelectric surfaces under thermal cycling using scanning force microscopy

Physical Review B, 2002

Scanning force microscopy in the dynamic contact mode with resonance enhanced domain contrast is ... more Scanning force microscopy in the dynamic contact mode with resonance enhanced domain contrast is applied to study in situ pattern formation and relaxation kinetics of ferroelectric domains on the cleavage surface of triglycine sulfate subjected to successive annealing-cooling cycles. Substantial differences in the domain morphology and kinetics are disclosed upon cooling at temperatures close to Tc. Convolution of stripe domains with residual domain nuclei and random pinning forces due to intrinsic defects are suggested to account for variations in the domain structure and slowing down of domain kinetics.

Manipulation of the vibration of cold ground-state Cesium molecules

Creating in an efficient way, a large and dense sample of ultracold molecules in their fundamenta... more Creating in an efficient way, a large and dense sample of ultracold molecules in their fundamental ground state, i.e. with neither vibration nor rotation, is an important step toward the realization in further experiments. Among them, cold collisions, controlled chemistry, or accurate spectroscopic measurement. One further motivation is the possibility to go towards the realization of a Bose-Einstein molecular condensate. But all existing experiments of cold molecules (Feshbach resonance, photoassocation) formed molecules in high vibrational state, mostly close to the dissociation limit. We want to explore different schemes to create or transfer cold molecules (Cs2) to the electronical and vibrational fundamental state (^1sigmag^+ v=0). We have studied the photoassociation of cold atoms in a high vibrational level (^1sigmag^+ or ^3sigmau^+) follow by an optical pumping scheme. We use a shaped femtosecond laser to realize the optical repumping step in order to excite the molecules to...

Anomalous doppler-free lineshapes in the saturation spectroscopy of cesium at 852 nm

Proceedings of 5th European Quantum Electronics Conference, 1994

Observation of fluorescence from high-lying states of potassium in a sodium-potassium mixture upon resonant laser excitation

Optics Communications, 1981

Fluorescence from three of the highly excited states of K (6S, 5P, and 4D) has been observed in a... more Fluorescence from three of the highly excited states of K (6S, 5P, and 4D) has been observed in a mixed vapour of sodium and potassium upon irradiation of two cw dye lasers tuned to the D resonance lines of sodium and potassium. Processes that may populate these levels via K*(4P) + Na*(3P) collisions are discussed.

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Second-harmonic apertureless near-field optical microscope

2005 Quantum Electronics and Laser Science Conference, 2005

We demonstrate apertureless near-field optical imaging with material contrast on metal nanostruct... more

Conformational Evolution of Elongated Polymer Solutions Tailors the Polarization of Light-Emission from Organic Nanofibers

Macromolecules, Jan 22, 2014

Polymer fibers are currently exploited in tremendously important technologies. Their innovative p... more Polymer fibers are currently exploited in tremendously important technologies. Their innovative properties are mainly determined by the behavior of the polymer macromolecules under the elongation induced by external mechanical or electrostatic forces, characterizing the fiber drawing process. Although enhanced physical properties were observed in polymer fibers produced under strong stretching conditions, studies of the process-induced nanoscale organization of the polymer molecules are not available, and most of fiber properties are still obtained on an empirical basis. Here we reveal the orientational properties of semiflexible polymers in electrospun nanofibers, which allow the polarization properties of active fibers to be finely controlled. Modeling and simulations of the conformational evolution of the polymer chains during electrostatic elongation of semidilute solutions demonstrate that the molecules stretch almost fully within less than 1 mm from jet start, increasing polym...

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Scanning probe microscope with interchangeable AFM-FFM and STM heads

Il Nuovo Cimento D, 1993

... M. ALLEGRINI(2), E. ARPA(3), C. ASCOLI(1), P. BASCHIERI(3), F. DINELLI(1), C. FREDIANI(i), M.... more

Broadband Vibrational Cooling of Cold Cesium Molecules: Theory and Experiments

Chinese Journal of Chemical Physics, 2009

The use of a broadband, frequency shaped femtosecond laser on translationally cold cesium molecul... more The use of a broadband, frequency shaped femtosecond laser on translationally cold cesium molecules has recently demonstrated to be a very efficient method of cooling also the vibrational degree of freedom. A sample of cold molecules, initially distributed over several vibrational levels, has thus been transfered into a single selected vibrational level of the singlet X 1 Σ g ground electronic state. Our method is based on repeated optical pumping by laser light with a spectrum broad enough to excite all populated vibrational levels but limited in its frequency bandwidth with a spatial light modulator. In such a way we are able to eliminate transitions from the selected level, in which molecules accumulate. In this paper we briefly report the main experimental results and then address, in a detailed way by computer simulations, the perspectives for a "complete" cooling of the molecules, including also the rotational degree of freedom. Since the pumping process strongly depends on the relative shape of the ground and excited potential curves, ro-vibrational cooling through different excited states is theoretically compared.

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In-situ spectroscopic analysis for pulsed laser deposition of superconductive Y-Ba-Cu-o thin films

High Tc Superconductor Thin Films, 1992

Some applications

High Resolution Spectroscopy of Atomic Hydrogen: Measurement of the Rydberg Constant

Real-time monitoring of mass migration on the free surface of azo-based polymer films via near field microscopy

International Quantum Electronics Conference, 2005., 2005

Laser diode spectroscopy of cesium vapor

The study of InGaN SQW materials with Polarization Modulation SNOM

2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, 2006

Abstract: We investigate on the photoluminescence spatial unhomogeneities of InGaN/GaN interface ... more

Cross-section measurement and theoretical evaluation for the energy-transfer collision Na(3P)+Na(3P)→Na(4F)+Na(3S)

Physical Review A, 1985

We have measured the cross section sigma(4F) for the collisional process Na(3P)+Na(3P)-->Na(4F... more We have measured the cross section sigma(4F) for the collisional process Na(3P)+Na(3P)-->Na(4F) +Na(3S). The experiment is based on the measurement of the intensities for 4F, 4D, and 3P fluorescence emissions in sodium vapor excited with a cw dye laser. sigma(4F) is determined relative to sigma(4D), which has been measured in an absolute way in previous experiments. Influence on sigma(4F) and sigma(4D) of the energy-transfer process Na(4F) +Na(3S)&rlarr2;Na(4D)+Na(3S) is also discussed. A theoretical evaluation of sigma(4F) and sigma(4D) relative to a chosen molecular channel is given and compared with the experimental determinations.

Force Gradient Versus Distance Curves Studied by Atomic Force Microscopy

Micro/Nanotribology and Its Applications, 1997

Normal and Lateral Forces in Friction Force Microscopy

Forces in Scanning Probe Methods, 1995

<title>Stabilization of amphiphilic block copolymer nanotubes and vesicles by photopolymerization</title>

Micro- and Nanotechnology: Materials, Processes, Packaging, and Systems III, 2006

We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either... more We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. Stabilized membranes of nanotubes and vesicles were formed by the directed selfassembly of poly(ethylene oxide)-block-polybutadiene, followed by photopolymerization, initiated by UV light, to a maximum double bond conversion of 15%. The photopolymerized nanotubes are extremely robust. The applicability of photopolymerization for biophysics and bioanalytical science is demonstrated by electrophoresing DNA molecules through a stabilized nanotube with an integrated vesicle reservoir.

Energy transfer collisions in laser excited mixtures of alkali vapors

AIP Conference Proceedings, 1989