Chiroptical Imaging of Crystals

First Principles Simulations of Optical Rotation of Chiral Molecular Crystals

“…This is because linear birefringence can mask the circular birefringence that is directly related to the OR. [43][44][45]47,62 The optic axis is a special direction where the linear birefringence is zero. 62 Therefore, in certain cases, we reoriented the tensor along the optic axis as also discussed in Ref.…”

“…Furthermore, it is possible to measure the OR of crystals along multiple directions, which avoids the issue of spatial averaging of the relevant tensor and provides more terms to compare with theory. 8,[40][41][42][43][44][45][46] From a practical standpoint, this is a significant advantage because spatial averaging implies the sum over the diagonal elements of the OR tensor; however, these elements have opposite sign and their sum is typically much smaller in magnitude. Thus, small errors in these diagonal elements can lead to large errors in the isotropic OR, which has often plagued direct comparison between theory and experiment in isotropic media.…”

Interference-contrast optical activity: a new technique for probing the chirality of anisotropic samples and more

“…Optical rotation, circular dichroism and other manifestations of optical activity are measured routinely for isotropic samples, serving as hallmarks of chirality in applications ranging from the determination of sugar concentrations to the investigation of virus structures [1][2][3][4]. By contrast, measurements of optical activity are seldom reported for anisotropic samples, the main reason being that anisotropic samples usually exhibit linear birefringence, linear dichroism and other effects that convolve with and partially suppress optical activity [5][6][7][8][9]. According to one source: 'Measuring [optical rotation] and [circular dichroism] in crystals of arbitrary symmetry has for two centuries been likened to the search for a needle in a haystack.…”

“…For this reason, we know virtually nothing from experiment about the orientational dependence of chiroptics of molecules, an enormous hole in the science of molecular chirality.' [9].…”

“…In what follows, we describe two possible versions of ICOA explicitly; one designed to probe the optical rotation of a transparent sample regardless of the sample's linear birefringence (ICOA-OR) and another designed to probe gradients in the optical rotation of a transparent sample (ICOA-GOR). ICOA-OR and ICOA-GOR are distinct from all polarimetric techniques known to the authors at the time of writing, including HAUP-based techniques [7,10,11,13,14], existing polarization interferometry techniques [15], optical heterodyne polarimetry [16,17], Metripol-based techniques [7,18], CRDP and other such cavity-based techniques [19][20][21] and Mueller matrix polarimetry [9,22]. ICOA-GOR, in particular, has elements in common with, but is subtly distinct from, DIC-based techniques [23][24][25][26][27][28][29].…”