Publications de Andrea Callegari

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We report here a measurement of electric dipole moments in highly vibrationally excited HDO molecules. We use photofragment yield detected quantum beat spectroscopy to determine electric field induced splittings of the J=1 rotational levels of HDO excited ...

We use infrared-visible double resonance overtone excitation to prepare HOCl molecules in single, well-characterized rotational levels of high OH stretching states just above the dissociation threshold on the ground potential energy surface. Combined with time-resolved laser induced fluorescence (LIF) detection of the OH product, this approach allows us to monitor the dependence of unimolecular dissociation rate on the angular momentum (J,K-a,K-c), total energy, and vibrational character of the state of the

We use infrared-visible double resonance overtone excitation to promote HOCl molecules to single, well-characterized rotational levels of high OH stretching states just above the HOCl-->HO+Cl dissociation threshold on the ground potential energy surface. Double resonance spectra are monitored by laser induced fluorescence detection of the OH dissociation products. We present here the results obtained in the 6 nu(1) region of (HOCl)-Cl-35 where we have studied states with J ranging from 4 to 25, K-a from 0 t

We present here the analysis of experimental Stark effect measurements made using photofragment quantum beat spectroscopy on the 14,0->, 15,0->, 18,0+> and 14,0-> 12 > vibrational states of H2O [Callegari, A.; et al. Science 2002, 297, 993.]. To link the m ...

The intensity of water absorption in the region of the solar spectrum plays a dominant role in atmospheric energy balance and hence strongly influences climate. Significant controversy exists over how to model this absorption accurately. We report dipole moment measurements of highly vibrationally excited water, which provide stringent tests of intensities determined by other means. Our measurements and accompanying calculations suggest that the best currently available potential and dipole surfaces do not

Mitotic bookmarking transcription factors remain bound to chromosomes during mitosis and were proposed to regulate phenotypic maintenance of stem and progenitor cells at the mitosis-to-G1 (M-G1) transition. However, mitotic bookmarking remains largely unex ...

This paper describes a new spectroscopic technique which uses photodissociation to detect pure rotational transitions in highly excited vibrational energy levels of the ground electronic state. This method has initially been applied to the (HOCl)-Cl-35 molecule in its second excited OH stretching vibration, the (200) state. In addition to observing the microwave signal, the Stark effect for this transition provides a dipole moment measurement in the (200) vibrational state. The (200) 18(0,18) --> 17(1,17) t

The authors measured the ultrafast response of triangular silver nanoparticles upon femtosecond excitation of their plasmon resonance. After a fast electron relaxation, the signature of a bimodal mech. vibration of the particle is apparent as a spectral mo ...

Pulsed laser excitation and photofragment detection methods are used to observe the 17(0,17)

We use infrared-visible double-resonance overtone excitation to prepare HOCl molecules in single, well-characterized rotational levels of the high OH stretching states v(OH) = 7 and v(OH) = 8. This work extends our recent studies on HOCl dissociation dynamics to higher energies above the dissociation threshold on the ground potential energy surface. In spite of a rapid increase of the vibrational coupling with v(OH), unimolecular dissociation is still limited by the rate at which energy initially deposited

We have developed a simple and accurate method for calibrating the amplitude of vibration of quartz tuning fork sensors commonly used in at. force- and near field optical-microscopy. Unlike interferometric methods, which require a complex optical setup, th ...

We describe a microwave-optical double resonance experiment designed for Stark effect measurements on molecules in excited vibrational energy levels of ground electronic states. This technique, which employs pulsed laser excitation and laser induced fluorescence detection, has been used to measure electric dipole moments in the 1(1), 5(1), and 5(2) vibrational states of formaldehyde. In addition, a Stark induced quantum beat experiment is briefly described. (C) 2003 American Institute of Physics.

The authors used light to transform a colloidal soln. of spherical silver nanoparticles into larger nanoparticles of a different shape. The particle size and shape can be controlled by choosing the wavelength(s) of light used to drive the photochem. growth. These findings suggest a new way of thinking about growth of nanoparticles in soln. and show the exciting possibility that light can be used as a major control parameter in metallic nanoparticle growth reactions. [on SciFinder (R)]

This article presents recent work investigating the unimolecular dissociation rates of quantum state-selected molecules. Such studies provide the most stringent test for quantitative models of unimolecular reactions and their assumptions. After briefly reviewing the various experimental and theoretical techniques for state-resolved unimolecular dissociation rates, we present results obtained in our laboratory using the method of double resonance overtone photofragment spectroscopy. We focus on the unimolecu

The authors studied ultrafast relaxation of localized excited states at Ge-related O deficient centers in SiO2 using femtosecond transient-absorption spectroscopy. The relaxation dynamics exhibits a biexponential decay, which the authors ascribe to the dep ...

We present the results of an exptl. and theor. study on the optimum design of shear-force sensors, used in scanning probe microscopes. We have optimized a configuration consisting of a tuning-fork/fiber-tip assembly, achieving quality factors (Q) exceeding ...

Andrea Callegari

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Dipole moments of HDO in highly excited vibrational states measured by Stark induced photofragment quantum beat spectroscopy

State-to-state unimolecular reaction dynamics of HOCl near the dissociation threshold: The role of vibrations, rotations, and IVR probed by time- and eigenstate-resolved spectroscopy

The spectroscopy and intramolecular vibrational energy redistribution dynamics of HOCl in the v(OH)=6 region, probed by infrared-visible double resonance overtone excitation

Dipole Moment of Water in Highly Vibrationally Excited States: Analysis of Photofragment Quantum-Beat Spectroscopy Measurements Using a Local-Mode Hamiltonian

Dipole moments of highly vibrationally excited water

A role for mitotic bookmarking of SOX2 in pluripotency and differentiation

Photodissociation detection of microwave transitions in highly excited vibrational states

Time-Resolved Photodynamics of Triangular-Shaped Silver Nanoplates

The dipole moment of HOCl in v(OH)=4

Eigenstate-resolved unimolecular dissociation dynamics of HOCl at v(OH)=7 and 8

A simple and accurate method for calibrating the oscillation amplitude of tuning-fork based AFM sensors

Fluorescence detected microwave Stark effect measurements in excited vibrational states of H2CO

Photochemically Grown Silver Nanoparticles with Wavelength-Controlled Size and Shape

State-to-state unimolecular reaction dynamics of highly vibrationally excited molecules

Relaxation processes of point defects in vitreous silica from femtosecond to nanoseconds

Q-factor optimization of a tuning-fork/fiber sensor for shear-force detection