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First choice for
STOPPED FLOW reaction analysis 300 °C
100 °C
-
20 °C
Figure 9. Phase change erasable media (EM) make use of lattice changes in metailic films, such as this Ag-Zn photochromic system. Other EM systems use crystalline to amorphous phase changes or bilayer phase changes
only weakly absorbing at the wavelengths obtainable from most solidstate diode lasers. Instead of using brute force laser power, one approach uses a tellurium coating V4 wavelength thick on a highly reflective aluminum surface, so that destructive interference makes the film look "black" to the radiation source. The rotation speed of commercial 12-in. disks (Thompson-CSF and Optimem) is 1122 rpm, with 14,500 TPI
and 15,300 BPI, and a transfer rate of about 0.5 MBPS- Figure 8 shows the disk's construction. Using a laser head and actuator, such as shown in Figure 6, rotational latencies are 54 ms and head latencies are 250 ms. LDs are therefore much slower than Winchester technology. However, within a 40track limit, the mirror servo shown can access a 1-Mbyte band in 5 ms. The 1-Gbyte disks are divided into 40,000 tracks, each with 25 1-Kbyte
Union Giken apparatus achieves a dead time as short as Vz millisecond for measurement of fast reactions. Gas pressure is directly applied to the surface of the reactants in each reservoir, mixing and flow being controlled from the end of the system by a high-response stop valve. The RA-401 STOPPED FLOW SPECTROMETER is the ideal match for fast reactions.
Photodetector
Analyzer Diode laser
Half-silvered mirror
i
The RA-451 D A T A PROCESSOR generates a simulated reaction curve from the measured results and automatically calculates the rate constant.
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Polarizer Lens
3200 m sec .1600 a f l e '
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530 nm
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The RA-415 RAPID SCAN A T T A C H MENT monitors the change in absorp tion spectrum during the reaction.
Curie point or compensation point medium
Weak
Other attachments are available for T-jump, P-jump, fluorescence and flash photolysis.
magnetic field
coil Figure 10. Curie-temperature-based EM disks rely on a writing laser to raise the temperature of the medium to the Curie point in a small area
Contact the sole export agent for more details:—
The coercivity drops, and the area can be magnetically oriented in a preferred direction by a weak electromagnet. The data are read back by a Kerr or Faraday effect subsystem. These use a polarized light beam from a diode laser. As this beam is reflected from the magnetic domains in the media, the plane of polarization is altered. This can be detected by a polarizer-analyzer
7-23, 5 chome Shimbashi, Minato-ku, Tokyo 105, Japan Telex: 28421 Cable: TAGOA T O K Y O Phone: (03) 432-8741
ATAGO BUSSAN CO., LTD.
CIRCLE 2 ON READER SERVICE CARD ANALYTICAL CHEMISTRY, VOL. 57, NO. 6, MAY 1985 · 705 A
