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author:("makkal, Anna")
1.  The LaueUtil toolkit for Laue photocrystallography. II. Spot finding and integration 
Journal of Synchrotron Radiation  2012;19(Pt 4):637-646.
A spot-integration method is described which does not require prior indexing of the reflections. It is based on statistical analysis of the values from each of the pixels on successive frames, followed for each frame by morphological analysis of initial masks to identify appropriate reflection footprints. The results are compared with those of the seed-skewness method which is based on minimizing the skewness of the intensity distribution within a peak’s integration box.
A spot-integration method is described which does not require prior indexing of the reflections. It is based on statistical analysis of the values from each of the pixels on successive frames, followed for each frame by morphological analysis to identify clusters of high value pixels which form an appropriate mask corresponding to a reflection peak. The method does not require prior assumptions such as fitting of a profile or definition of an integration box. The results are compared with those of the seed-skewness method which is based on minimizing the skewness of the intensity distribution within a peak’s integration box. Applications in Laue photocrystallography are presented.
doi:10.1107/S0909049512022637
PMCID: PMC3380659  PMID: 22713901
photocrystallography; X-ray diffraction; X-ray detection; CCD; Laue method; spot integration; background estimate; statistical analysis; image filtering
2.  Restricted Photochemistry in the Molecular Solid State: Structural changes on Photoexcitation of Cu(I) Phenanthroline metal-to-ligand-charge-transfer (MLCT) complexes by Time-Resolved Diffraction 
The journal of physical chemistry. A  2012;116(13):3359-3365.
The excited state structure of [Cu(1)[(1,10-phenanthroline-N,N’) bis(triphenylphosphine)] cations in their crystalline [BF4] salt has been determined at both 180 and 90K by single-pulse time-resolved synchrotron experiments with the modified polychromatic Laue method. The two independent molecules in the crystal show distortions on MLCT excitation which differ in magnitude and direction, a difference attributed to a pronounced difference in the molecular environment of the two complexes. As the excited states differ, the decay of the emission is bi-exponential with two strongly different lifetimes, the longer lifetime, assigned to the more restricted molecule, becoming more prevalent as the temperature increases. Standard deviations in the current Laue study are very much lower than those achieved in a previous monochromatic study of a Cu(I) 2,9 dimethyl-phenanthroline substituted complex (J. Am. Chem. Soc. 2009, 131, 6566), but the magnitude of the shifts on excitation is similar, indicating that lattice restrictions dominate over the steric effect of the methyl substitution. Above all the study illustrates emphatically that molecules in solids have physical properties different from those of isolated molecules and that their properties depend on the specific molecular environment. This conclusion is relevant for the understanding of the properties of molecular solid state devices which are increasingly used in current technology.
doi:10.1021/jp300313s
PMCID: PMC3545449  PMID: 22385365
3.  The LaueUtil toolkit for Laue photocrystallography. I. Rapid orientation matrix determination for intermediate-size-unit-cell Laue data 
Journal of Applied Crystallography  2011;44(Pt 6):1182-1189.
A new method for determination of the orientation matrix of Laue X-ray data is presented. The method is based on matching of the patterns of central reciprocal lattice rows projected on a unit sphere centered on the origin of the reciprocal lattice of the Laue data set with the corresponding pattern of a monochromatic data set on the same material.
A new method for determination of the orientation matrix of Laue X-ray data is presented. The method is based on matching of the experimental patterns of central reciprocal lattice rows projected on a unit sphere centered on the origin of the reciprocal lattice with the corresponding pattern of a monochromatic data set on the same material. This technique is applied to the complete data set and thus eliminates problems often encountered when single frames with a limited number of peaks are to be used for orientation matrix determination. Application of the method to a series of Laue data sets on organometallic crystals is described. The corresponding program is available under a Mozilla Public License-like open-source license.
doi:10.1107/S0021889811038143
PMCID: PMC3246831  PMID: 22199400
LaueUtil; Laue photocrystallography; orientation matrix determination; computer programs
4.  The development of Laue techniques for single-pulse diffraction of chemical complexes: time-resolved Laue diffraction on a binuclear rhodium metal-organic complex 
A modified Laue technique suitable for time-resolved diffraction is described in which profile-independent integration is used, the RATIO method is applied and multi-crystal data are normalized to a common scale. The method is applied in single-pulse pump–probe studies of a binuclear Rh complex, showing Rh—Rh bond shortening of 0.136 (8) Å on excitation.
A modified Laue method is shown to produce excited-state structures at atomic resolution of a quality competitive with those from monochromatic experiments. The much faster data collection allows the use of only one or a few X-ray pulses per data frame, which minimizes crystal damage caused by laser exposure of the samples and optimizes the attainable time resolution. The method has been applied to crystals of the α-modification of Rh2(μ-PNP)2(PNP)2 (BPh4)2 [PNP = CH3N(P(OCH3)2)2, Ph = phenyl]. The experimental results show a shortening of the Rh—Rh distance in the organometallic complex of 0.136 (8) Å on excitation and are quantitatively supported by quantum-mechanical (QM)/molecular-mechanics (MM) theoretical calculations which take into account the confining effect of the crystal environment, but not by theoretical results on the isolated complex, demonstrating the defining effect of the crystal matrix.
doi:10.1107/S0108767311011883
PMCID: PMC3121236  PMID: 21694470
Laue techniques; single-pulse diffraction; quantum-mechanical/molecular-mechanics calculations; QM/MM calculations; time-resolved X-ray crystallography
5.  Time-resolved Laue diffraction of excited species at atomic resolution: 100 ps single-pulse diffraction of the excited state of the organometallic complex Rh2(μ-PNP)2(PNP)2 ·BPh4 
The polychromatic Laue technique has been applied in 100 ps delay synchrotron pump–probe experiments of the triplet excited state of a Rh(I) dinuclear complex. The observed contraction of the Rh–Rh distance of 0.154 (13) Å is less than predicted by a series of theoretical calculations, a difference attributed to the constraining effect of the crystal lattice.
doi:10.1039/c0cc04997b
PMCID: PMC3129623  PMID: 21210070

Results 1-5 (5)