Analytical probes capable of mapping molecular composition at the nanoscale are of critical importance to materials research, biology and medicine. Mass spectral imaging makes it possible to visualize the spatial organization of multiple molecular components at a sample's surface. However, it is challenging for mass spectral imaging to map molecular composition in three dimensions (3D) with submicron resolution. Here we describe a mass spectral imaging method that exploits the high 3D localization of absorbed extreme ultraviolet laser light and its fundamentally distinct interaction with matter to determine molecular composition from a volume as small as 50 zl in a single laser shot. Molecular imaging with a lateral resolution of 75 nm and a depth resolution of 20 nm is demonstrated. These results open opportunities to visualize chemical composition and chemical changes in 3D at the nanoscale.

We report the demonstration of an amplitude-division soft-x-ray interferometer that can be used to generate high-contrast interferograms at the wavelength of any of the saturated soft-x-ray lasers (5.6 -46.9 nm) that are available at present. The interferometer, which utilizes grazing-incidence diffraction gratings as beam splitters in a modif ied Mach -Zehnder conf iguration, was used in combination with a tabletop 46.9-nm laser to probe a large-scale ͑ϳ2.7-mm-long͒ laser-created plasma.

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We have directly probed the conditions in which the Ni-like Pd transient collisional x-ray laser is generated and propagates by measuring the near-field image and by utilizing picosecond resolution soft x-ray laser interferometry of the preformed Pd plasma gain medium. The electron density and gain region of the plasma have been determined experimentally and are found to be in good agreement with simulations. We observe a strong dependence of the laser pump-gain medium coupling on the laser pump parameters. The most efficient coupling occurs with the formation of lower density gradients in the preformed plasma and when the duration of the main heating pulse is comparable to the gain lifetime ͑ϳ10 ps for mid-Z Ni-like schemes͒. This increases the output intensity by more than an order of magnitude relative to the commonly utilized case where the same pumping energy is delivered within a shorter heating pulse duration ͑Ͻ3 ps͒. In contrast, the higher intensity heating pulses are observed to be absorbed at higher electron densities and in regions where steep density gradients limit the effective length of the gain medium. A detailed understanding of the plasma that constitutes the gain medium is crucial for the development of efficient x-ray lasers. Use of the prepulse technique has allowed x-ray lasers to achieve saturated output using many different elements for the lasing media ͓1͔. However, even the best laser-pumped x-ray lasers typically have an efficiency of 10 −6 . In the transient collisional excitation ͑TCE͒ scheme a low intensity long pulse preforms a plasma, which is allowed to expand and cool before being heated by a high intensity short pulse ͓2͔. This short pulse, in some cases with subpicosecond duration, rapidly heats the plasma to generate a high gain coefficient, saturated x-ray laser output ͓3͔, and x-ray laser pulses as short as 2 ps ͓4͔. In experiments reported on high power laser drivers the pulse duration of the short pulse generated by chirped pulse amplification ͑CPA͒ is in the range of 0.3-3 ps ͓3-7͔. It has been assumed to some extent that by maximizing the intensity of the main heating pulse the temperature, collisional pumping, and local gain coefficient will also be maximized. Under these conditions the lowest saturated wavelength currently demonstrated is 7.3 nm for Nilike Sm ͓5͔.To improve the efficiency we need to better understand the laser-plasma coupling and plasma characteristics of the x-ray laser media. In this paper we combine the techniques of near-field imaging with recently developed picosecond x-ray laser interferometry ͓8͔ to characterize the lasing medium for a Ni-like Pd x-ray laser. It is observed that a combination of controlling and reducing the plasma density gradients while matching the duration of the main pumping pulse to the gain lifetime at a specific density optimizes the coupling efficiency. This increases the x-ray laser output by an order of magnitude over the case where the same pumping energy is delivered into a higher intensity, shorter pulse. In contr...

The formation and evolution of a collisional aluminum plasma jet created by optical laser irradiation of triangular grooves with pulses of 120ps duration at an intensity of 1x10(12)W cm(-2) were studied with experiments and simulations. Series of high-contrast soft x-ray laser interferograms obtained with a 46.9nm laser mapped the plasma density evolution of an initially narrow plasma jet that expands along the symmetry plane and evolves into a broader plasma plume with significant side lobes. Two-dimensional simulations performed using the radiation hydrodynamic code HYDRA reveal that the jet formation is initiated by accelerated material ablated from the vertex and is augmented by the continual sequential arrival of wall material along the symmetry plane, where it collides and is redirected outward. Radiative cooling is identified as an important process in maintaining the collimation of the jet. These results demonstrate that well collimated collisional plasma jets with parameters in a range of interest can be generated with low-energy laser pulses (<1J) , opening the possibility of studying relevant plasma phenomena in a small laboratory setting.