Introduction: Coronary magnetic resonance angiography (MRA) has been performed on 3.0T to generate higher SNR compared to 1.5T. In addition, high blood-to-myocardium contrast could be achieved using the SSFP technique [1]. However, SSFP is highly sensitive to field inhomogeneities. In particular, signal nulls occur every 1/TR in resonance frequency, producing “banding” artifacts in images. With...

The evolution of the pulse centroid velocity of the Poynting vector for both ultrawideband rectangular and ultrashort Gaussian envelope pulses is presented as a function of the propagation distance in a dispersive, absorptive dielectric material. The index of refraction of the material is described by the Lorentz-Lorenz formula in which a single-resonance Lorentz model is used to describe the m...

We study multi-shot intensity-and-phase measurements of unstable trains of ultrashort pulses using twodimensional spectral shearing interferometry (2DSI). We find that, like other interferometric ultrashort-laser pulse-measurement methods, it measures only the coherent artifact and so yields effectively only a lower bound to the pulse length. We also attempt to identify warning signs of pulse-s...

We calculate the dynamics and the radiation emitted from free electrons in an ultrashort pulsed laser focus. In a Gaussian focus, at low electron densities for which space charge is negligible, we find that ponderomotive forces limit the effective volume of radiation emission to a region that is much smaller than the focal waist and even significantly smaller than the fundamental wavelength. Co...

The photoassociation process shows strong dependence on the temporal duration of the electromagnetic eld pulses and their frequencies. This dependence is investigated using quantum mechanical simulations that include all ranges of impact parameters and contributions from bound-to-bound transitions. The photoassociation yield of mercury atoms to produce excimer dimers is enhanced for short (ps) ...

Indeed, to see the action in any fast event, whether it’s a computer chip switching states, dynamite exploding, or a simple soap bubble popping, requires a strobe light with a shorter duration in order to freeze the action. But then to measure the strobe-light pulse requires a light sensor whose response time is even faster. And then to measure the light-sensor response time requires an even sh...

Diffractive optics fabrication is performed by two complementary processing methods that rely on the photoablation of materials by ultrashort UV laser pulses. The spatially selective ablation of materials permits the direct microetching of high-quality surface-relief patterns. In addition, the direct, spatially selective transfer of the ablated material onto planar and nonplanar receiving subst...

The coherent interaction with ultrashort light pulses is a powerful strategy for monitoring and controlling the dynamics of wave packets in all states of matter. As light presents an oscillation period of a few femtoseconds (T=2.6 fs in the near infrared spectral range), an external optical field can induce changes in a medium on the sub-cycle timescale, i.e. in a few hundred attoseconds. In ...

The interaction of sub-picosecond laser pulses with magnetically ordered materials has developed into an extremely exciting research topic in modern magnetism. From the discovery of sub-picosecond demagnetization over a decade ago to the recent demonstration of magnetization reversal by a single 40 fs laser pulse, the manipulation of spins by ultrashort laser pulses has become a fundamentally c...

The origin of the coherences in two-dimensional spectroscopy of photosynthetic complexes remains disputed. Recently, it has been shown that in the ultrashort-pulse limit, oscillations in a frequency-integrated pump-probe signal correspond exclusively to electronic coherences, and thus such experiments can be used to form a test for electronic vs. vibrational oscillations in such systems. Here, ...