178 research outputs found
Nuclear spin conversion in formaldehyde
Theoretical model of the nuclear spin conversion in formaldehyde (H2CO) has
been developed. The conversion is governed by the intramolecular spin-rotation
mixing of molecular ortho and para states. The rate of conversion has been
found equal 1.4*10^{-4}~1/s*Torr. Temperature dependence of the spin conversion
has been predicted to be weak in the wide temperature range T=200-900 K.Comment: REVTEX, 16 pages + 5 eps figure
New access to very weak interactions in molecules
It is predicted that nuclear spin conversion in molecules can be efficiently
controlled by strong laser radiation resonant to rovibrational molecular
transition. The phenomenon can be used for substantial enrichment of spin
isomers, or for detection of very weak (10-100 Hz) interactions in molecules.Comment: REVTEX, 11 pages + 4 eps figure
Enrichment of CH3F nuclear spin isomers by resonant microwave radiation
Theoretical model of the coherent control of nuclear spin isomers by
microwave radiation has been developed. Model accounts the M-degeneracy of
molecular states and molecular center-of-mass motion. The model has been
applied to the 13CH3F molecules. Microwave radiation excites the para state
(J=11,K=1) which is mixed by the nuclear spin-spin interaction with the ortho
state (9,3). Dependencies of the isomer enrichment and conversion rates on the
radiation frequency have been calculated. Both spectra consist of two
resonances situated at the centers of allowed and forbidden (by nuclear spin)
transitions in the molecule. Larger enrichment, up to 7%, can be produced by
strong radiation resonant to the forbidden transition. The spin conversion rate
can be increased by 2 orders of magnitude at this resonance.Comment: REVTEX, 14 pages + 6 eps figure
Coherent control of enrichment and conversion of molecular spin isomers
A theoretical model of nuclear spin conversion in molecules controlled by an
external electromagnetic radiation resonant to rotational transition has been
developed. It has been shown that one can produce an enrichment of spin isomers
and influence their conversion rates in two ways, through coherences and
through level population change induced by radiation. Influence of conversion
is ranged from significant speed up to almost complete inhibition of the
process by proper choice of frequency and intensity of the external field.Comment: REVTEX, 13 pages + 6 eps figure
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