GLOSSARY
A
Absolute configuration
The spatial arrangement of the atoms comprising a chiral molecule or group. More details here.
Achiral
Not chiral.
Amino acid dating
Anomalous x-ray scattering
A definitive technique for determining absolute configuration.
Asymmetric/asymmetrical
Not symmetric/not symmetrical.
Asymmetric carbon
A carbon atom bonded to four different types of atom or groups of atom. More details here.
B
Biological homochirality
The empirical observation that the molecular building blocks of life show consistent preferences for one chirality over the other; L amino acids rather than D amino acids, D sugars rather than L sugars etc.
c
Cahn-Ingold-Prelog priority rules
A convention for ascribing either an "(S)" descriptor or an "(R)" descriptor to an asymmetric carbon. More details here.
Circular birefringence
A difference in refraction for left- and right-handed circularly polarised electromagnetic waves (eg visible light). An example of optical activity. Gives rise to optical rotation.
Circular dichroism
A difference in absorption for left- and right-handed circularly polarised electromagnetic waves (eg visible light). An example of optical activity.
Circular differential photoacoustic spectroscopy
Circular polarisation of luminescence
Circular dichroism manifest in spontaneous emission rather than absorption.
Chiral/chirality
An entity is said to be "chiral" and have "chirality" if it differs from its mirror-image form. Derived from the Greek word for hand. Coined by Lord Kelvin.
Chiral rotational spectroscopy
A hybrid optical/microwave spectroscopic technique for chiral molecules.
Chiroptical (technique)
An optical technique with chiral sensitivity, eg optical rotation.
Cotton effect
The anomalous optical rotatory dispersion and circular dichroism seen together near an absorption resonance.
CRS
Stands for "chiral rotational spectroscopy".
D
Dextro rotatory
Clockwise optical rotation as seen when looking towards light source, ie positive specific rotation. See also laevo rotatory.
e
Enantiomer
One of a pair of distinct mirror-image objects. Usually 'small'; a chiral molecule, for example.
Enantiomorph
One of a pair of distinct mirror-image objects. Usually 'large'; a chiral crystal, for example.
Enantiomeric excess
A measure of the relative numbers of enantiomers in a sample. See here for more details.
Enantiomorphic excess
Analogous to enantiomeric excess but for 'large' chiral objects rather than 'small' ones. Used by Cameron in ICOA.
f
Faraday effect
Synonymous with Faraday rotation.
Faraday rotation
Optical rotation induced by a static magnetic field. See here for more details.
Fluorescence detected circular dichroism
The indirect measurement of circular dichroism via a corresponding difference in fluorescence intensities excited by left- and right-handed circular polarisations of light. Useful for samples with poor transmission, eg biological samples.
g
Gyrotropy
A synonym of optical activity?
H
Helicity
The projection of a particle's spin along the particle's direction of motion.
Heterochely
The projection of a particle's spin along the particle's direction of motion.
Hyper Rayleigh optical activity
Blah.
I
ICOA
An acronym for "interference-contrast optical activity".
ICOA-OR
An acronym for "interference-contrast optical activity", as applied to the measurement of optical rotation.
ICOA-GOR
An acronym for "interference-contrast optical activity", as applied to the measurement of optical rotation gradients.
ij infra zilches
A set of conserved properties of the free electromagnetic field. First described in (Cameron12a).
J
Jeremy (the lefty snail)
A garden snail with a shell that coiled to the left rather than to the right.
K
Kuhn dissymmetry factor (or ratio)
A measure of circular dichroism.
L
Laevo rotatory
Anticlockwise optical rotation as seen when looking towards source of light, ie negative specific rotation. See also dextro rotatory.
M
Magnetic optical rotation
Synonymous with the Faraday effect.
Magnetic circular dichroism
Differential absorption of left- and right-handed circular polarisations of light induced by a a static magnetic field. A manifestation of optical activity.
"M" descriptor
Used to describe the absolute configuration of a chiral molecule with an apparent left-handed helical structure. The "M" stands for "minus". See also "P" descriptor.
N
N
N.
O
OAM
Stands for "optical angular momentum" or "orbital angular momentum", usually in the form of helical phase fronts.
Octant rule
Used to interpret the signs and magnitudes of the Cotton effects induced in a chirally perturbed carbonyl chromophore.
Optical activity
A difference in response to left- and right-handed circular polarisations of light.
Optical rotation
The rotation of the azimuth of polarised light. Exhibited naturally by chiral samples and certain achiral anisotropic samples. Can be induced in all samples by a magnetic field; see the Faraday effect.
Optical rotatory dispersion
The variation of optical rotation as a function of frequency (or wavelength).
ORD
An acronym for "optical rotatory dispersion".
P
"P" descriptor
Used to describe the absolute configuration of a chiral molecule with an apparent right-handed helical structure. The "P" stands for "plus". See also "M" descriptor.
Polarimetry
The measurement of polarisation changes induced by a sample, eg optical rotation.
Q
Q
Q
R
Racemate
Racemization
"(R)" descriptor
One of two possible descriptors attributable to a chiral centre according to the Cahn-Ingold-Prelog priority rules; see also "(S)" descriptor. The "R" stands for "rectus". More details here.
S
"(S)" descriptor
One of two possible descriptors attributable to a chiral centre according to the Cahn-Ingold-Prelog priority rules; see also "(R)" descriptor. The "S" stands for "sinister". More details here.
Snapshot circular dichroism
A multiplexed approach towards the measurement of circular dichroism.
Specific ellipticity
The ellipticity induced by a sample due to circular dichroism (or circular extinction), normalised by density and path length.
Specific rotation (aka specific optical rotatory power)
The optical rotation induced by a sample, normalised by density and path length.
Specific optical rotatory power
A synonym of specific rotation.
T
Tyrian purple
The colour of a purple dye made using sea snails.
U
U
U
V
Verdet's law
The relationship between Faraday optical rotation, material properties embodied by the Verdet constant, magnetic field strength and the relative orientation of magnetic field and light propagation direction.
Vibrational optical activity
Optical activity deriving from the vibrational degrees of freedom of e.g. a chiral molecule. Examples of vibrational optical activity include VCD and ROA.
Vibrational circular dichroism
Is this a thing?
W
White-light polarimetry
The measurement of optical rotation using a continuous spectrum of visible (ie white) light. Described in (Anderson19).
X
X-ray scattering
The scattering of x-rays from e.g. the lattice planes of a crystal. Used with anomalous x-ray scattering to determine absolute configuration.
Y
YTILARIHC.COM
This lovely website. Note that "ytilarihc" is "chirality" spelled backwards.
Z
Zilch
A set of ten (nine independent) conserved properties of the electromagnetic field in vacuum, first described in (Lipkin64a). Higher-order versions of optical helicity, optical spin and the ij infra zilches, as explained in (Cameron12a).
REFERENCES
(Anderson19a) J Anderson, C Gillen, J Wright, C S Adams & I G Hughes 2019 Optical rotation of white light Am. J. Phys. 88 247-251
(Cameron12a) R P Cameron, S M Barnett & A M Yao 2012 Optical helicity, optical spin and related quantities in electromagnetic theory New J. Phys. 14 053050
(Lipkin64a) D M Lipkin 1964 Existence of a new conservation law in electromagnetic theory J. Math. Phys. 5 696-700