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The laser-induced demagnetization of a ferromagnet is caused by the temperature of the electron gas as well as the lattice temperature. For long excitation pulses, the two reservoirs are in thermal equilibrium. In contrast to a picosecond laser pulse, a femtosecond pulse causes a non-equilibrium between the electron gas and the lattice. By pump pulse length dependent optical measurements, we fi...

We studied the spatial and temporal distributions of ionic, neutral, and molecular species generated by femtosecond laser produced plasma under varying ambient nitrogen gas pressures. Plasmas were generated by irradiating planar graphite targets using 40 fs pulses of 800 nm radiation from a Ti:Sapphire laser. The results show that in the presence of an ambient gas, the molecular species spatial...

Laser-driven, quasimonoenergetic electron beams of up to approximately 200 MeV in energy have been observed from steady-state-flow gas cells. These beams emitted within a low-divergence cone of 2.1+/-0.5 mrad FWHM display unprecedented shot-to-shot stability in energy (2.5% rms), pointing (1.4 mrad rms), and charge (16% rms) owing to a highly reproducible gas-density profile within the interact...

A simple model for laser ablation plasma plume expansion in a background gas is presented. The expanding plume is approximated by a semi-ellipsoidal shell of infinitesimal thickness and with a mass corresponding to the amount of background gas that has been snowploughed by the shell as it expands. Furthermore, the internal pressure of the plume and external pressure of the background gas are ta...

The evolution features of lithium plasma generated by two different schemes viz. the laser-blow-off (LBO) of multicomponent LiF-C thin film and conventional laser ablation referred to here as laser produced plasma (LPP) from solid lithium have been studied using fast imaging and optical emission spectroscopic techniques. Modifications of the plume structure in different experimental conditions ...

The discharge characteristics of the XeF* (B~X) laser are investigated. The NF3 and Xe partial pressure of the laser gas mixture and the total gas pressure have been varied. A highest specific output energy of 4.7 J/1 with an efficiency of 0.5% was obtained from a X-ray preionized Ne/Xe/NF3 gas mixture at 6 bar with single-pulse excitation through a multichannel spark gap. PACS: 42.55.Gp, 42.60...

Diode laser absorption spectroscopy provides a direct method of determinating species concentration and local gas temperature in combustion flames. Under microgravity conditions, diode lasers are particularly suitable, given their compact size, low mass and low power requirements. The development of diode laser-based sensors for gas detection in microgravity is presented, detailing measurements...

We report the observation of rotational Bloch oscillations in a gas of nitrogen molecules kicked by a periodic train of femtosecond laser pulses. A controllable detuning from the quantum resonance creates an effective accelerating potential in angular momentum space, inducing Bloch-like oscillations of the rotational excitation. These oscillations are measured via the temporal modulation of the...

A laser-based in-situ spectrometer using near infrared diode laser at 767 and 770 nm to detect potassium atoms in high-temperature environments is described. The device was used to investigate the thermal dissociation of KCl and to monitor K behind the flue gas filter (300mm diameter, 1000°C) of a 250kW-coal combustor, without the necessity of error prone gas sampling. With a response time of 2...