Grating-tuned, single-longitudinal-mode, diode-pumped Nd:YVO4 laser

NRC publication: Ye

Relativistic channel formation with different pulse durations

Relativistic channels are generated in an under-dense plasma by means of subpicosecond laser pulses. The channel extension is characterized via the Thomson-scattered light and the impact of the laser pulse duration and chirp are studied. It is shown that, under certain conditions, the channel extends further when the pulse duration is increased. This is in contrast to many earlier reports, where the channel grows with increasing laser power. Some theoretical arguments are presented to support the experimental findings. The number of electrons, accelerated in the forward direction, and their energies are assessed. In some cases, it is found that the channel divides and the fragments extend in different directions. This raises the question if, and how, the channel formation can be externally manipulate

Influence of laser pulse duration on relativistic channels

A high-power (10 TW) laser is employed to generate relativistic channels in an underdense plasma. The lengths of the channels are measured by imaging the Thomson-scattered light, and the gas densities are determined through the forward Raman scattered light. The laser-pulse parameters are varied and their impact on the channel formation is studied. It is found that increasing the laser pulse duration in many cases produces longer channels, even as this implies reducing the laser peak power. A theoretical discussion is presented, proposing an explanation of the experimental results. (C) 2002 American Institute of Physics

Lifetime measurements on the c '(1)(4)Sigma(+)(u), v=0, 1 and 2 states of molecular nitrogen

Excited state lifetimes of c(4)('1)Sigma (+)(u), upsilon = 0-2 states of molecular nitrogen have been determined in a laboratory investigation using a picosecond XUV laser in a pump-probe configuration. For c(4)('1)Sigma (+)(u) upsilon = 0 the lifetime is tau = 740 +/- 50 ps, for the lowest rotational states. For higher rotational states a gradual shift towards tau = 495 ps is found in agreement with previous findings that these states are subject to predissociation. For c(4)(') Sigma (+)(u) upsilon = 1 no J-dependence is found and values for two isotopomers are reported: tau = 240 ps for (NN)-N-14-N-15 = 240 ps for (NN)-N-14-N-15. For c(4)('1)Sigma (+)(u) upsilon = 2 a lifetime for the lowest rotational states (J = 0-3) was derived: tau = 675 +/- 50 ps; for J = 11 a lifetime of tau less than or equal to 120 ps is deduced. All values for the lifetimes including the J-dependences are explained in a model based on Rydberg-valence interaction. (C) 2001 Elsevier Science B.V. All rights reserved