A new multispectral imaging microscope with micrometer spatial resolution and millisecond temporal resolution has been developed. The imaging microscope is based on the use of an acousto-optic tunable filter (AOTF) for spectral tuning and a progressive scan camera capable of snapshot operation for recording. It can operate in two modes: images are recorded as a function of time or wavelength. When operated as a function of time, the microscope is configured so that as many images as possible are recorded, grabbed, and stored per one wavelength. Upon completion, the AOTF is scanned to a new wavelength, and a new set of images are recorded. Up to 33 images/ second (i.e., 30 ms/image) can be recorded in this mode. In the other configuration, the recording wavelength is rapidly scanned (by means of the AOTF) and only one image is rapidly recorded, grabbed, and stored for each wavelength. Because additional time is needed to scan the AOTF, the maximum number of images can be grabbed in this case is 16 frames/s. Preliminary applications of the imaging microscope include measurements of photoinduced changes of a single unit cell in temperature-sensitive cholesteric liquid crystals as a function of time and wavelength. The changes were found to be varied with time and wavelength. Interestingly, the photoinduced changes of unit cells in the liquid crystal are not the same but different from cell to cell. This imaging microscope is particularly useful for measurements of small-size samples that undergo rapid chemical or biochemical reactions, e.g., activities of a single biological cell.
Laserspectroscopic investigations of the Stark splitting and shift behaviour of the hyerfine components of resonance lines of potassium, rubidium, europium and gallium have been performed in external electric fields up to field strengths of 400 kV/cm. For the transitions 39 K(4 2 S 1/2 − 4 2 P 1/2 ; D 1 -line); λ = 769.896 nm, 39 K(4 2 S 1/2 − 4 2 P 3/2 ; D 2 -line); λ = 766.490 nm, 85,87 Rb(5 2 S 1/2 − 5 2 P 1/2 ; D 1 -line); λ = 780.023 nm, 151,153 Eu(a 8 S 7/2 − z 6 P • 7/2 ); λ = 576.520 nm, 69,71 Ga(4s 2 4p 2 P 3/2 − 4s 2 5s 2 S 1/2 ); λ = 417.204 nm, we derived the scalar polarizability difference ∆α 0 between upper and lower level of the transitions and the individual tensor polarizabilities α 2 .
Abstract. Performing laser-atomic beam spectroscopy, we have remeasured the transition frequencies and the fine structure splitting of the lithium, sodium and potassium resonance lines. Additionally, the isotope shifts 6Li-VLi could be determined with high accuracy. Transition frequencies were determined by means of a high-precision lambdameter working at vacuum conditions, calibrated by saturation absorption of 12712 . Frequency differences up to 1 THz could be determined with the help of a carefully calibrated marker etalon with systematical errors smaller than 1 MHz.
A new multispectral imaging spectro meter with millisecond resolution has been developed. This instrument is based on the use of an acousto-optic tunable lter (AOTF) for spectral tuning and a simple progressive scan cam era capable of snapshot operation for recording. The fast multispectral imaging can be performed in two con gurations: recording images as a function of tim e or as a function of wavelength. In the rst con guration, multiple images are recorded , grabbed, and stored per one wavelength. Upon completion, the AOTF is scanned to a new record ing wavelength and a new set of images are recorded. It was found that, in this con guration, the imaging spectrom eter is capable of recording, grabbing, and storing up to 33 images per s (i.e., 30 ms per image). Because an external signal is used to start the event and the recording of images, and the period between the start of the event and the recording and grabbing of im ages can be appropriately adjusted by a delay line, the time reso lution of the spectrometer is not limited to 30 ms but rather can be adjusted to a shorter or longer time scale. In the second con guration, the reco rding wavelength is rapidly scanned (by the AOTF) and only one image is rapidly recorded, grabbed, and stored for each wavelength. Because additional time is needed to scan the AOTF, the maximum number of images that can be grabbed in this case is 16 fram es per s. Prelim inary applications of the imaging spectrometer include measurements of photoinduced changes in temperature-sensitive cholesteric liquid crystals as a function of tim e and wavelength. It was found that irradiating with a near-infrared (NIR) diode laser of 805 nm led to changes in the liquid crystal. The changes were found to vary with time and wavelength, namely, at about 360 ms after the NIR laser pulse the liquid crystal underwent changes in the visible region around 570 nm. The changes shifted toward longer wavelength concomitantly with time; i.e., maximum change at about 600 ms shifted to 718 nm.
We have shown on a simple model that the anisotropy of collisions induced by a -polarized RF field may lead to the reduction of relaxation rate of the linearpolarized light observed along the axis of anisotropy. In the simplest case of j"1 of the excited state the difference with the isotropic case may reach 20% of the relaxation constant of alignment.
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