Ultrafast dynamics after nuclear reactions

[Nagy Denes Lajos]

Dear Sergey,

the methods you are looking for are Mossbauer emission spectroscopy and
in-beam Mossbauer spectroscopy. Admittedly, these methods can only be used
if the nuclear reaction leads to a Mossbauer transition. By default, the
time scale of the techniques is the lifetime of the excited nuclear level
of the Mossbauer transition. E.g., the electron capture of 57Co
(indirectly) leads leads to the 14.4-keV level of 57Fe, which has a
lifetime of 141 ns. Therefore the "Mossbauer window" is open from about
10^-8 s to about 10^-6 s and, accordingly, one can see directly only
atomic changes that are neither faster nor slower than this range.

The time scale of the atomic changes ranges from about 10^-15 s to minutes
or even longer. In metals, due to the high concentration of conduction
electrons, the non-equilibrium distribution of electrons relaxes very fast
and no after effects of the nuclear reaction can bee seen in an emission
Mossbauer experiment. In contrast to this, a great variety of electronic
after effects have been observed in insulators and semiconductors. These
include anomalous (aliovalent) charge states, anomalous spin states and
non-equilibrium population of low-lying electronic levels.

It is sometimes possible to study indirectly electronic after effects that
are much faster than the Mossbauer lifetime. In fact, by studying the
magnetic field, temperature, carrier concentration, etc. dependence of the
average population of the electronic states during the Mossbauer time
window, one may be able to determine some parameters of much faster
precursor electronic states including crystal field parameters.

You may wish to consult a few papers on Mossbauer emission spectroscopy
and references therein:

1. R. Doerfler et al., Phys. Rev. Lett. 57(1986)2849-2852.

2. H. Spiering et al., Hyp. Int. 53(1990)113-142.

3. D.L. Nagy, Hyp. Int. 83(1994)3-19.

4. T. Becze-Deak et al., J Phys.: Cond. Matter 11(1999)6239-6250.

With best regards,

D.L. Nagy

   *******************************************************************
   *    Prof. Denes Lajos Nagy                                       *
   *                                                                 *
   *                    KFKI Research Institute for Particle and     *
   *                    Nuclear Physics,                             *
   *                    Department of Nuclear Physics,               *
   *                    H-1525 Budapest, P.O.B. 49., Hungary         *
   *                                                                 *
   *                    Tel.:      +36 1 392 2517                    *
   *                    Fax:       +36 1 392 2518 or                 *
   *                               +36 1 392 2598                    *
   *                    E-mail:    nagy at rmki.kfki.hu                 *
   *                    Web page:  http://www.kfki.hu/~nagyd/        *
   *******************************************************************


On Thu, 10 Jan 2002, Sergey Egorov wrote:

> Dear Colleagues,
> When nuclear reaction occur, for example neutron
> capture,  electron structure of an atom significatly
> changes. Does anybody aware of the experimental
> research on the ultrafast dynamic of atomic changes
> after nuclear reaction? What is the time scale of
> these events? Is it possible to observe, for example,
> dynamics of optical spectra changes after nuclear
> reaction?
>
> Thank you,
> Dr. Sergey Egorov
> Research Scientist
> Del Mar Ventures
> http://www.sciner.com/
>
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> etc.
>
>
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  *******************************************************************
  *  Denes Lajos Nagy  KFKI Research Institute for Particle and     *
  *                    Nuclear Physics,                             *
  *                    Department of Nuclear Physics,               *
  *                    H-1525 Budapest, P.O.B. 49., Hungary         *
  *                                                                 *
  *                    Tel.:      +36 1 392 2517                    *
  *                    Fax:       +36 1 392 2518 or                 *
  *                               +36 1 392 2598                    *
  *                    E-mail:    nagy at rmki.kfki.hu                 *
  *                    Web page:  http://www.kfki.hu/~nagyd/        *
  *******************************************************************