PARAHYDROGEN Meaning and
Definition
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Parahydrogen is a term used in the field of physics and chemistry to refer to a specific form or isotopologue of molecular hydrogen (H2). It is an isomer of common hydrogen, orthohydrogen. The difference lies in the spin states of the two hydrogen nuclei (protons) within the molecule.
In its ground state, orthohydrogen has two protons with parallel spins, resulting in a net nuclear spin of 1. On the other hand, parahydrogen is characterized by the two protons having antiparallel spins, leading to a net nuclear spin of 0. This distinction in spin states has significant implications for various properties and behaviors.
One important application of parahydrogen is in the field of magnetic resonance imaging (MRI). Due to its spin configuration, parahydrogen exhibits a longer relaxation time compared to orthohydrogen. This unique feature enables efficient polarization transfer to other molecules during the process of hyperpolarization, enhancing the sensitivity of MRI experiments.
Additionally, parahydrogen has been widely studied in the area of quantum mechanics and reaction dynamics, as its distinct spin states affect collisional and chemical reactions involving molecular hydrogen. The specific spin selection rules associated with parahydrogen play a crucial role in the observable outcomes of these reactions.
In summary, parahydrogen is an isotopologue of molecular hydrogen with two protons having antiparallel spins, resulting in a net nuclear spin of 0. It possesses unique properties that are important in applications such as MRI and in understanding quantum mechanical and chemical reactions involving hydrogen.
Etymology of PARAHYDROGEN
The word "parahydrogen" is derived from the Greek prefix "para-" meaning "beside" or "alongside", and the term "hydrogen". "Para-" is often used in chemistry to denote an isomer or a form of a molecule that is similar to another but has a different arrangement or orientation of its atoms. In the case of parahydrogen, it refers to a specific spin isomer of molecular hydrogen (H2), distinguished from the more common orthohydrogen isomer. The distinction is based on the different spins (nuclear spins) of the hydrogen nuclei in the molecule.
