R-AXIS RAPID. X-ray Single Crystal Structure Analysis System. Product Information

Transcription

1 The Rigaku Journal Vol. 15/ number 2/ 1998 Product Information X-ray Single Crystal Structure Analysis System R-AXIS RAPID 1. Introduction X-ray single crystal structure analysis is known as the easiest and most direct approach to investigating the structure of the solid state. Rigaku has marketed four-circle X-ray diffractometer systems (AFC) as a standard analysis tool in this field for many years. Rigaku has also been offering imaging-plate-mounted two-dimensional X-ray diffractometers (R-AXIS series), designed for protein structure analysis, as a high-speed data collection system for small molecules. Now, aiming primarily at small molecule single crystal structure analysis, Rigaku has developed a new instrument, the IP-mounted Weissenberg camera R-AXIS RAPID. Other area detector systems typically use MoKa radiation for small molecule analysis in order to compress the diffraction data because of the limited apertures of these instruments. The cylindrical geometry of the IP in the R-AXIS RAPID extends the scanning range (2θ) to 140, allowing measurement of complete data sets using CuKα radiation. A newly developed software package unifies the equipment control and data processing functions, so that even a novice can collect data for structure analysis without a detailed knowledge of crystallography. The imaging plate employed is of a type characterized by high sensitivity and low noise, so even exceedingly small crystals can be measured in a short time, thus meeting broad analytical needs from general users and professionals alike. 2. Features (1) The X-ray tube assembly and the goniometer are combined into a single unit to make intense incident X-rays obtainable. (2) The user may choose either a sealed tube or a rotating anode X-ray source, depending on the intended use and budget. 43 The Rigaku Journal

2 (3) As shown in Fig. 1, a newly developed 3 χ goniometer permits automatic axial alignment. High-speed measurement by the screenless Weissenberg method is practicable in addition to oscillation photography. (4) A broad scanning range of -60 to ±140 in the circumferential direction and ±45 in the axial direction is obtained by the use of a cylindrical imaging plate. Accordingly, a complete data set suitable for publication in Acta Crystallographica C can be measured with not only MoK α but also CuKα radiation. (5) The vertical arrangement of the IP makes a compact system with good access to the sample. (6) A high-speed readout system significantly reduces the dead time. (7) The double photomultiplier system has attained a sensitivity of 1 x-ray photon/pixel and a dynamic range of 10 6 or more and less than 1 x- ray photon of read noise. (8) Automatic measurement can be made using newly developed software. Fig Hardware Specifications X-ray generator X-ray generator Sealed tube Rotating anode Max. rated output 3 kw 18 kw X-ray shutter Rotary shutter Dimensions 570W x 1560 H x 780 D mm 600 W x 1700 H x 1000 D mm X-ray tube Mo, Cu (optional) Camera section System Vertical Weissenberg camera Monochromator Flat graphite crystal Camera length mm Angle measuring range -60 ~ +144 (circumferential direction) ± 45 (axial direction) Collimator 0.3 mm, 0.5 mm, 0.8 mm double pinhole Beam stopper To be installed right behind crystal CCD camera for sample observation ¼ color, to be displayed on host CPU Goniometer System 3-axis Eulerian goniometer ω -85 ~ +265 (in steps) χ -15 ~ +55 (in steps) φ -180 ~ +360 (in steps) Axial intersection precision Within φ20µm Vol. 15 No

3 IP readout system Readout system Internal circumference readout (optics rotation) system Number of IPs Detection area One 465 mm x 258 mm Pixel size 100 x 100 µm; 100 x 150 µm; 200 x 200 µm Number of pixels 4500 x 2560; 4500 x 1700; 2250 x 1280 Output data Readout time Excitation light source Detector Readout sensitivity 23MB; 16MB; 6MB 100 sec; 70 sec; 50 sec Semiconductor laser (max. Rated output 30 mw) Dual photomultiplier 1 x-ray photon/pixel Dynamic range 1 ~ 10 6 (0 ~ ) IP erase time Duty time 20 sec 140 sec (at 100 x100 µm) Controller Function X-ray exposure, readout, sequence control of data transfer IP data readout Interface for control Interface for data High-speed 16 bits linear ADC RS232C SCSI2 Dimensions 900 W x 1950 H x 1000 D mm 1050 W x 1950 H x 1000 D mm Host CPU IRIS O2 CPU Main memory Magnetic disk Auxiliary memory Magnetic tape Display Laser printer Computer desk Host CPU dimensions 64 bits RISC (R5000) or equivalent 96 MB 2GB (for system) + 4GB (for data) 4-time speed CD-ROM drive (built-in) 2GB DAT drive 17 monitor Printer that can handle postscript Computer desk, chair, table top...one each 800 W x 1270 H x 730 D 4. Software The newly developed fully automatic data collection software AUTO incorporates both equipment control and data processing functions together. As a result, the measuring conditions can be automatically determined, allowing inexperienced scientists to collect useful diffraction data. Measurement and data processing will follow consecutively. Fig. 2 shows a flowchart of measurement. The operator has only to mount a sample and enter certain measuring conditions and the sequence of processing 45 The Rigaku Journal

4 AUTO FUNCTION Crystal centering, sample name entry, etc while watching CCD camera Determination of setting matrix from two photos of ω=0~5 and ω =90~95, respectively Osc/weiss: For user s prior selection; Determination of optimal measurement conditions from setting matrix and lattice constants; Calculation of completeness and redundancy. Oscillation photo mode: Measurement of ~44 photos for an ordinary sample Weissenberg mode: ~10 Start of measurement based on conditions automatically determined by Strategy; Automatic determination of box size for integrated reflection intensity calculation; Refinement of setting matrix, lattice constant, etc; Integrated reflection intensity merge: post refine: laue: scale: abscor: average: Merge of intensity data file per frame Refinement of crystal parameters, e.g. Lattice constants Determination of Laue class Determination of scale factor per frame Absorption correction Averaging and output of equivalent reflections Structure analysis (Optional) Fig. 2. Flowchart of automatic measurement steps from Index to Scale will then be executed automatically. 5. Measurement Example Fig. 3 shows the measurement of cytidine (C 9 H 13 O 5 N 3 ) with the R-AXIS RAPID. This example shows the results of the oscillation photographic method and the screenless Weissenberg method, using both CuKα and MoKα radiations as the X-ray source. In the Weissenberg method, exposure is made by slowly moving the IP which is synchronized with the crystal rotation (ω-axis oscillation) so as to prevent overlap of diffraction spots. As may be seen from Fig. 3(A) and (C), this method is a very efficient one which permits recording of large quantities of diffracted X-rays on a single IP exposure. Because the axis used for axial alignment is automatically Vol. 15 No

5 (A) Oscillation photo, MoKα, 60kV-50mA oscillation angle: 5, exposure time: 5 min (B) Oscillation photo, CuKα, 50kV-40mA oscillation angle: 30, exposure time: 5 min (C) Weissenberg photo, MoKα, 60kV-50mA oscillation angle: 40, exposure time: 20 min (D) Weissenberg photo, CuKα, 60kV-50mA oscillation angle: 60, exposure time: 5 min Fig. 3. X-ray diffraction pattern in each measurement mode (sample: cytidine C 9 H 13 O 5 N 3 ) Table 1. Characteristics of each measurement mode (rough measurement time required for ordinary crystals is indicated in parentheses) Oscillation photographic method MoKα Most standard method (3~8 hrs) Strong diffraction intensity CuKα Crystal with large lattice parameters (~50 C) Absolute structure determination by Anomalous dispersion effect (6~12 hrs) Weissenberg method High-speed measurement (1~4 hrs) High-speed measurement in above conditions (4~8 hrs) determined in the software from the result of Index the operator can be freed from complicated axial alignment work, unlike in the conventional Weissenberg method. CuK α radiation interacts more strongly with samples than does MoKα radiation, and therefore displays higher performance in the measurement of tiny crystals. When Fig. 3(A) and (B) are compared, it may be seen that CuK α radiation may be used to measure crystals having low diffracting power or large lattice constants (50 C or so) because it has a longer wavelength than MoKα radiation. CuKα radiation excels, furthermore, in determination of absolute structure by utilizing the anomalous dispersion effect. Table 1 shows the characteristics of each measurement mode. 47 The Rigaku Journal

6 Fig. 4 shows the structure analysis results of cytidine (C 9 H 13 O 5 N 3 ) measured by the Weissenberg method using MoKα radiation. The measurement time was 60 minutes. In this case, the measurement conditions were determined assuming that the crystal system is triclinic. If the Laue class is known, the measurement time can be reduced further. Sample Cytidine (C9H13O5N3) Crystal size 0.3 x 0.3 x 0.4 X-ray source Measurement Exposure time Lattice Constant Crystal System Laue Class MoK α 50 kv 48 ma Weissenberg method 10 sec/deg (Total 60 min) orthorhombic mmm Rmerge 3.2% R 2.9% Rw 3.0% Fig. 4. Structure analysis result Vol. 15 No