Antonella Lai

Hard x-ray contact microscopy with 250nm spatial resolution using a LiF film detector and a tabletop microsource

An innovative route for deep-submicrometer spatial resolution hard x-ray microscopy with tabletop x-ray source is proposed. A film of lithium fluoride (LiF) was used as imaging detector in contact mode. We present here the x-ray images recorded on LiF films of a Fresnel zone plate with submicrometer gold structures and of an onion cataphyll. The images were read with an optical confocal microscope in fluorescence mode. The measured spatial resolution was about 250nm, i.e., close to the resolution limit of the confocal microscope. The advantages and drawbacks, and the possible improvements, of this route are discussed.

Scanning near-field optical microscopy images of microradiographs stored in lithium fluoride films with an optical resolution of λ∕12

Here we show a new, simple method to observe soft x-ray microradiographs of biological material. A thin film of lithium fluoride (LiF) works as image detector, storing the microradiograph obtained exposing biological samples to extreme ultraviolet and soft x-ray radiations. To read the stored image, collecting the optically stimulated visible luminescence emitted by the LiF active color centers locally produced by the x rays, a scanning near-field optical microscope is used with an optical aperture of 50nm, i.e., λ∕12, where λ is the wavelength of the collected photoluminescence.

Detection of ethylene traces by photoacoustic spectroscopy

A laser based photoacoustic system has been designed and built at ENEA in order to monitor bio-gases produced in different processes involving living cells. Experiments aimed to reveal traces of ethylene emitted from tomato plantlets and fruits under temperature stress are here presented and discussed.

Lithium fluoride coloration by laser-plasma soft x-rays: a promising tool for x-ray microscopy and photonics

A new imaging detector for EUV or soft-X-ray radiation based on optically stimulated luminescence (OSL) of lithium fluoride (LiF) films or crystals is presented. The first micro-radiography images of biological samples and of meshes obtained on LiF using a laser-plasma source or an X-ray laser are shown, and (up to now) a resolution better than one micron is demonstrated. The dependence of the coloration density vs the deposited X-ray dose is considered and the advantages of this new diagnostic technique for both coherent and non-coherent EUV sources, compared with CCDs detectors, photographic films and photoresists are discussed. This new detector is extremely suitable for laser plasmas and for X-ray lasers sources.

Micro-Radiographs Stored in Lithium Fluoride Films Observed by Scanning Near-Field Optical Microscopy

A new simple method to get soft X-ray micro-radiographs of biological material with a spatial resolution reaching 50 nm is described. A thin film of lithium fluoride (LiF) works as image detector, storing the micro-radiograph obtained exposing biological material to Extreme Ultra-Violet and soft X-ray radiations. Scanning near-field optical microscope (SNOM) is used to read the micro-radiograph at nanometric resolution up to λ/12, collecting the fluorescence ( λ=650 nm) excited by an Ar+ laser light ( λ=458 nm).

Laser photoacoustic spectroscopy: A powerful tool for measurement of trace gases of biological interest at sub-ppb level

A high sensitive photoacoustic system has been developed to monitor trace gases released by biological samples at concentrations of sub-ppb level. We have applied this technique to measure the release of the plant hormone ethylene during seed germination and ripening of climacteric fruits and of the marker ethylene as a result of doping cultures of human cells with heavy metals, of damaging living organisms by ionising radiation(X-ray)and of unleashing lipid peroxidation in lung epithelium following the inhalation of cigarette smoke.

Laser photoacoustic system for characterization of climacteric and nonclimacteric fruits in postharvest

The emission of ethylene from climacteric fruit banana (Musa x paradisiaca L.) and non climacteric fruits lemon (Citrus limon Burm. F.) at different stages of ripening (from a few days after setting to full maturity stage) by the Laser Photoacoustic Spectroscopy System, developed in ENEA Frascati, was measured. A high ethylene production rate from mature banana fruit was found, as expected for climacteric fruit. Significant differences between ethylene emitted by the lemon after setting stage and by the young fruit were observed. Also ethylene emission from lemon fruits at different ripening stages (from light green to turning and full ripe) was detected. Depending on the ripening stage, differences in ethylene emission rates were found, although the emissions were low as expected for non-climacteric fruit.