Low-Temperature Physics and Chemistry in Cryomatrice
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Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
2000
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| Zitieren: | Low-Temperature Physics and Chemistry in Cryomatrice / V.E. Bondybey, E.V. Savchenko // Физика низких температур. — 2000. — Т. 26, № 9-10. — С. 859-862. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1860102671059386368 |
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| author | Bondybey, V.E. Savchenko, E.V. |
| author_facet | Bondybey, V.E. Savchenko, E.V. |
| citation_txt | Low-Temperature Physics and Chemistry in Cryomatrice / V.E. Bondybey, E.V. Savchenko // Физика низких температур. — 2000. — Т. 26, № 9-10. — С. 859-862. — англ. |
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| container_title | Физика низких температур |
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Low-Temperature Physics and Chemistry in Cryomatrice
(Preface)
Studies of materials at low temperatures had a
tremendous impact upon the development of physics
and science in general, and played a significant role
in the emergence and formulation of the quantum
theory at the beginning of the 20th century. The
earliest attempts at producing low temperatures in
the laboratory relied on the cooling effect resulting
from dissolution of crystalline solids in water. This
method was also employed in the works of Sir
Humphry Davy and Michael Faraday started in
1823, who succeeded in liquefying of a variety of
gases, and can thus be viewed as pioneers of cryo-
genic research. Studies of gases at low tempera-
tures, and the observation that their pressure de-
creases linearly with temperature led in 1848 Kelvin
to interpret temperature in terms of kinetic energy.
He introduced the concept of an absolute scale,
where zero corresponds to the temperature at which
constituent atoms and molecules lose all their ki-
netic energy.
A convenient path to cryogenic research was
opened up in 1850’s by the observations by Joule
and Thompson that gases expanding adiabatically
into vacuum have to overcome the weak attractive
forces between their atoms or molecules, which
results in their cooling. This method was used
around 1877 by Cailletet and Pictet to condense a
number of hard to liquefy gases, including oxygen,
nitrogen, and carbon monooxide, work which in
turn kindled the interest of Dewar in cryogenic
research. Among his accomplishments, besides in-
vention of the familiar «Dewar flask» was the
demonstration that oxygen is paramagnetic; he also
succeeded in 1898 in liquefying, and a year later in
solidifying hydrogen gas.
An important step in further development of the
field was the construction of the first cyclically
operating refrigerators based on the Joule-
Thompson effect around 1895 by Linde. This made
possible large scale liquefaction of air with distila-
tive separation of its components, and greatly facili-
tated cryogenic research. Finally, helium was lique-
fied in 1908 by Kamerlingh Onnes who cooled it by
liquid hydrogen below its inversion temperature
prior to the adiabatic Joule–Thompson expansion.
The history of low temperature physics is inti-
mately intertwined with the history of rare gases.
Lord Rayleigh, while making accurate measure-
ments of molecular weights (he wanted to check
Prout’s hypothesis that the atoms of various ele-
ments are built from hydrogen, and have therefore
weights that are integral multiples of its atoms)
noted that nitrogen obtained from atmospheric air
has a different weight than that made chemically.
The mystery was solved by Ramsay, who was in
1894 able to show that atmospheric nitrogen con-
tains a new element, the rare gas argon. Ironically,
argon was not the first of the rare gases to be
discovered. Some 25 years earlier Lockyer observed
during solar eclipse a strong yellow spectral line,
which he could not attribute to any known element.
Janssen then concluded, that this line is due to a
new chemical element, presumably present only on
the sun, and suggested therefore to name it helium.
One year after the discovery of argon, in 1895,
Ramsay was able to isolate helium on earth by
heating a mineral cleveite, where it forms due to
radioactive decay of uranium. These first two mem-
bers of the «inert» gas family, were soon followed
by neon, krypton and xenon, all produced by frac-
tionating liquefied air.
Interestingly, the realization of that rare gas
solids and other condensed gases may provide a
suitable medium for spectroscopic studies followed
very shortly after their discovery. Vegard at the
university of Leiden, at that time the Mecca of low
temperature research, started already in the early
1920’s a series of studies, which would clearly fall
into the area which is today called matrix isolation.
He investigated luminescence from condensed gases
irradiated by x-rays or electrons, in the hope of
gaining understanding of the origin of Aurora Bore-
alis and other atmospheric and stratospheric phe-
nomena. Using this method he was for instance the
first one to observe the au
3+ Xg
1+ phosphorescence
from the lowest triplet state of molecular nitrogen,
which is today known as the Vegard–Kaplan bands.
After a virtual gap of some thirty years, the
interest in spectroscopic studies in solid rare gases
resurfaced in the early 1950’s, when Pimentel
coined the phrase «matrix isolation» and when
deliberate, systematic studies of species isolated in
rare gas solids started. The major goal of matrix
isolation studies at that time was the observation
and characterization of highly reactive radicals and
other reaction intermediates. Such species which
otherwise under normal conditions have only a very
ephemeral existence, could be stabilized in the
rigid, inert solid, and studied then at leisure by
spectroscopic means. Over the next decade virtually
hundreds of free radicals, molecular ions, clusters,
and similar transient species were generated, de-
tected, and their molecular constants and other
properties determined in rare gas matrices.
The condensed rare gases are characterized by
weak interatomic interactions, and are therefore
usually found to perturb only weakly the isolated
«guest» species of interest. Furthermore, the guest
spectra in the low temperature solids are invariably
greatly simplified, since in most cases the molecular
rotation is quenched, so that the entire rotational
structure collapses into a sharp zero phonon line.
Furthermore, at the low temperatures typically only
the vibrationless level of the ground state of the
guest is populated, so that «hot bands» and «se-
quence bands» which often clutter gas phase spectra
are absent.
After an initial rapid development of the matrix
isolation field, in 1970’s alternative techniques were
developed for studies of transient species, which
completely avoid the medium perturbations inhe-
rent in the condensed phase technique. Thus for
instance ions, clusters or radicals could be produced
in electric discharges, by photolysis, or by laser
vaporization, cooled to a few K by an adiabatic
expansion, and investigated by laser spectroscopic
techniques in the gas phase. In addition to elimina-
ting the medium perturbation problem, such inves-
tigations also have the advantage of providing the
rotational information which is in general lost in
the nonrotating matrix isolated species, and for a
while they seemed to spell doom to the matrix
isolation technique.
In spite of that, however, if judged by the
number of publications and by the frequency of and
attendance at conferences on low temperature spec-
troscopy in solid matrices, one finds that the tech-
nique is still very much alive and well, only the
emphasis and goals of the matrix studies have in
many instances changed. Very often, the perturba-
tions and interactions of the guest with the solid
host, which were in the early works viewed as
bothersome drawbacks of the technique, now be-
come the main object and emphasis of the study. A
wide range of phenomena and elementary excita-
tions specific to condensed samples, such as pho-
nons, librons, excitons and neutral or charged so-
lute solvation become available for study. The low
temperatures and weak interatomic interactions in
the van der Waals solids often results in slowing
down various relaxation processes, and makes them
accessible to experimental study. The dynamics of
many processes are here not obscured by the much
stronger forces present in the more conventional
solids, which makes them easier to study experi-
mentally, and model theoretically.
We have mentioned above that the early experi-
mental studies in condensed rare gases originated in
Leiden, and matrix isolation was developed by
George Pimentel in California. On the other hand,
many key contributions towards understanding the
spectroscopy and physical properties of impurities
and defects in solids originated in the countries of
Eastern Europe, including for instance the Ukraine,
Russia, Estonia, and others. It is therefore perhaps
appropriate, that this collection of papers appears as
a special issue of «Fizika Nizkikh Temperatur», a
journal which was founded in the «B. Verkin Insti-
tute for Low Temperature Physics», and in which
many of these early important contributions first
appeared. The contributions in this issue were se-
lected to give what we hope to be a fair cross-sec-
tion of the current activities in this field, and
demonstrate the breadth of its applications.
Most of the early matrix isolation studies em-
ployed absorption spectroscopy, predominantly in
the infrared range, to characterize the samples, but
nowadays a much broader repertory of investigation
techniques has become available. The samples can
be studied at a wide range of wavelengths both in
absorption or emission, and they can be excited by
tunable or fixed frequency lasers in the infrared,
visible or UV, x-rays or electrons. Using picosecond
or femtosecond laser techniques, many processes
whose dynamics could previously only be indirectly
inferred from spectroscopic observations can now be
investigated in real time, as for instance exemplified
in the contribution by Chergui. Synchrotron radia-
tion is a particularly useful, widely tunable photon
source, which is increasingly being applied for mat-
rix studies, as exemplified by the nice EXAFS
investigation by Roubin et al., or by the work of
Kerins et al. on high lying states of Mg atoms in
matrices.
The applications of matrices today extend over
an extremely wide range of different fields ranging
from single molecules and microscopic properties of
solids to bulk properties of solids, or investigation
of reactions occurring in the interstellar space. The
matrix method is useful in static studies of defects
and impurities, and their effect upon the solid state
properties, as well as in studies of dynamics on
timescales ranging from days to femtoseconds. It
yields information about diffusion processes, chemi-
cal reactions and charge localization and charge
transfer. The information gained from these studies
860 Fizika Nizkikh Temperatur, 2000, v. 26, Nos. 9/10
is useful in varying and fields extending from
purely basic science to technologically important
fields such as chemical catalysis, semiconductor
technology, or laser physics.
Several papers included deal with the traditional
goal of matrix isolation, identification of new spe-
cies, but for their efficient generation are now often
employed novel methods, such as vaporization by
lasers, which were not available to the early pio-
neers in the field. Here one could name the papers
by Andrews et al. or by Lammers et al. Besides
optical spectroscopy, also EPR has traditionally
been a very useful technique, used to investigate
open shell radicals and their reactions, as nicely
demonstrated in the present issue by the manuscript
by Misochko et al. Another infrared work exempli-
fying application to species of astrophysical or at-
mospheric interest is the infrared investigation of
the photolysis of ozone by Chaabouni et al.
While traditional matrix materials were most
commonly argon or nitrogen, for a variety of rea-
sons much interest is currently shifting to other
solids, for instance solid hydrogen or helium, and
several of the manuscripts in this issue deal with
these hosts. In the first place, in these very light, so
called «quantum hosts» the zero point motion is not
negligible compared with the lattice constants and
separations of the host atoms, and consequently a
variety of «quantum effects» not present in the
conventional solids can be observed and studied. In
this issue the papers by Ganshin et al., Kiselev et
al. and Galtsov et al. deal with such quantum
solids. An additional advantage, particularly in the
case of parahydrogen, are the very sharp, high
resolution spectra which can often be observed. In
this collection, for instance the papers by Miki and
Momose, or by Tam and Fajardo take advantage of
this fact. The possibilities of producing «high ener-
gy density materials», and increasing for instance
the specific impulse of rocket fuels by stabilizing
atoms and reactive intermediates in solid hydrogen
were also widely discussed and increase the interest
in solid hydrogen or deuterium, and the study by
Danilychev and coworkers is relevant in this con-
text.
The specific nature of the trapping site, its sym-
metry, geometry, and its effects upon the guest
properties and spectroscopy are most often quite
unknown, and several of the contributions selected,
for instance the works by Roubin et al. or Lorenz et
al., explore this question. Conversely, the spectra of
an atomic or molecular guest whose spectroscopy is
well known in the gas phase may be greatly affected
by the host when isolated in the condensed matrix.
In this way the guest atom or molecule may be used
as a «spy» yielding information for instance about
the changes in the trapping site size and local
symmetry, and thus about the structural changes
and phase transitions occurring in the host solid
matrix, as nicely demonstrated here in the paper by
Minenko et al.
Inclusion of even very minor concentrations of
impurities can often have a profound effect upon the
optical, structural, and thermodynamic properties
of solids, and this issue and the detailed under-
standing of such effects is of key importance in
many technologically important areas such as for
instance semiconductor industry, solid state lasers
and many others. Rare gases, with their relatively
simple structure provide a very suitable medium for
investigating these effects. Such applications are
exemplified for instance by the thermal conductivi-
ties measurements of matrices doped with a rotating
impurity, such as methane in the article by Dudkin
et al. or by the sound propagation study by Kiselev
et al., and also the study by Freiman et al. on the
effect of oxygen impurities upon the cryocrystal
thermal and magnetic properties can be mentioned
in this context.
The rare gases, besides being a very convenient
systems for solid state theoretical modelling, have
themselves many potentially very useful charac-
teristics. Thus their optical properties, and in par-
ticular their transparence, extending from far infra-
red into the vacuum ultraviolet range, besides
enhancing their usefulness as a medium for spectro-
scopic matrix isolation studies, potentially also
makes them a suitable material for solid state lasers,
in particular in the far ultraviolet region. This
consideration makes the questions of optical gain,
stimulated emission and lasing in rare gas solids, as
investigated for instance in the contribution by
Chabbi et al., particularly interesting.
One of the drawbacks of the early matrix studies
was due to the fact that most methods of generating
transient species are not selective, but one typically
obtains a complex mixture of products, among
which the individual carriers have to be sub-
sequently identified, for instance by a series of
laborious isotopic substitution experiments. This
problem can be solved if the product of interest is
mass selected prior to deposition into the matrix.
While such deposition of mass selected species in
sufficient yields and concentrations for spectro-
scopic characterization represents a non-trivial task,
in the last few years several groups have made
considerable advances in this field, and in this issue
Fizika Nizkikh Temperatur, 2000, v. 26, Nos. 9/10 861
the papers by Fang et al. and by Lorenz et al.
describe experiments in this direction.
While rare gases were chosen as suitable matrix
isolation «solvents» for their chemical inertness, it
is now well known that they are not really inert,
but under suitable conditions display a relatively
rich chemistry. Since the early days in the Pimen-
tel’s laboratory, rare gas matrices also proved to be
a convenient reactive medium for the production,
stabilization and identification of rare gas com-
pounds. In the last few years there has been a
resurgence of activity in this field, and a wealth of
novel rare gas compounds has recently been de-
scribed, with the paper Lundell et al. exemplifying
this nice work.
As already noted above, the current range of
activities in the matrix isolation is quite broad, in
fact so broad that a single special issue can not do
it justice. Even the selection of topics and tech-
niques represented here is far from exhaustive. In
spite of these limitations and shortcomings, we hope
that it will demonstrate that even seventy five years
after its earliest beginnings, and some fifty years
after its rebirth in the Pimentel’s laboratory, matrix
isolation remains a very useful, versatile technique,
with a wide scope of applications. The chances are
good that it will probably easily survive also the
next fifty years, as well as most of its current
practitioners, and that also future generations of
chemists and physicists will, like George Pimentel
always used to recommend, try to «keep it cool».
V. E. Bondybey
E. V. Savchenko
862 Fizika Nizkikh Temperatur, 2000, v. 26, Nos. 9/10
|
| id | nasplib_isofts_kiev_ua-123456789-129206 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0132-6414 |
| language | English |
| last_indexed | 2025-12-07T17:29:50Z |
| publishDate | 2000 |
| publisher | Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України |
| record_format | dspace |
| spelling | Bondybey, V.E. Savchenko, E.V. 2018-01-16T18:44:02Z 2018-01-16T18:44:02Z 2000 Low-Temperature Physics and Chemistry in Cryomatrice / V.E. Bondybey, E.V. Savchenko // Физика низких температур. — 2000. — Т. 26, № 9-10. — С. 859-862. — англ. 0132-6414 https://nasplib.isofts.kiev.ua/handle/123456789/129206 en Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України Физика низких температур Preface Low-Temperature Physics and Chemistry in Cryomatrice Article published earlier |
| spellingShingle | Low-Temperature Physics and Chemistry in Cryomatrice Bondybey, V.E. Savchenko, E.V. Preface |
| title | Low-Temperature Physics and Chemistry in Cryomatrice |
| title_full | Low-Temperature Physics and Chemistry in Cryomatrice |
| title_fullStr | Low-Temperature Physics and Chemistry in Cryomatrice |
| title_full_unstemmed | Low-Temperature Physics and Chemistry in Cryomatrice |
| title_short | Low-Temperature Physics and Chemistry in Cryomatrice |
| title_sort | low-temperature physics and chemistry in cryomatrice |
| topic | Preface |
| topic_facet | Preface |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/129206 |
| work_keys_str_mv | AT bondybeyve lowtemperaturephysicsandchemistryincryomatrice AT savchenkoev lowtemperaturephysicsandchemistryincryomatrice |