PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Ways of the photoelectric effect; How physicists have learned how to select them

2013-12-19
(Press-News.org) Contact information: Ilya Usov
science-release@rector.msu.ru
Lomonosov Moscow State University
Ways of the photoelectric effect; How physicists have learned how to select them This work was recently published in Physical Review Letters.

In contrast to its apparent simplicity (that brought Einstein his Nobel Prize), the photoelectric effect, when an electron is knocked out from its parent atom by a photon, is quite complicated to analyze in general, especially when the atom contains a large number of electrons. Like the many-body problem in classical mechanics, the quantum many-body problem is very difficult to conceptualize and remains a serious challenge for theory. Hence, the principal role in this field is played by experiment. The latter, however, faces its own difficulties when it comes to unraveling data associated with the atomic photoeffect itself from a variety of other effects due to essentially irrelevant phenomena.

Not the least among the latter phenomenon is related to the spin (and thus the magnetic moment) of the atomic nucleus. It may be thought of as the quantum generalization of the angular momentum in classical mechanics, which is calculated as the product of the linear momentum (mass times velocity) of a particle and its position vector relative to the axis of rotation. Each proton and each neutron in the nucleus possess their own magnetic moment. While these moments tend to largely compensate each other, the resultant moment does not always have to vanish. Any residual moment, even though relatively small and hence its interaction with the electronic shell is labeled as "hyperfine", may dramatically influence the process of the photoelectron emission. A non-zero nuclear spin spoils the picture, in particular when the atom is excited, which is the reason for this case being of such strong interest for physicists.

A collaboration of seven physicists from Italy, France, Germany, and Russia chose to perform their study on xenon -- the element previously used to resolve mysterious features in the atomic photoeffect. Being a noble gas, xenon is very convenient for such studies: it does not form chemical bonds and does not contaminate the apparatus with its compounds. Even more important in the choice was that, among all the noble gases, only xenon has stable isotopes with both zero and non-zero nuclear magnetic moments. Furthermore, xenon is an interesting atom on his own rights, due to the large number of electrons and the associated complicated dynamics of its electron shells.

The experimental design suggested isotope separation with the help of a mass-spectrometer. Subsequently, each of the isotopes was excited with synchrotron radiation and simultaneously irradiated with a wavelength-tunable laser beam. All ejected electrons were counted and sorted by energy and scattering angle.

All this is easy to say, but reality is much more complicated. The first targets excited by synchrotron radiation were obtained in the late 1990s, but the principal difficulty was to combine two radiation beams, laser and synchrotron. Moscow theorist A. N. Grum-Grzhimailo, one of the collaborators, says that only a few people in the world are currently capable to solve this problem. One of them -- Michael Meyer from the European XFEL GmbH based in Hamburg (Germany) -- contributed to the experiment described above. The actual experiment was carried out using a unique beamline with variable polarization, maintained by the group of Laurent Nahon at the French synchrotron SOLEIL.

The role of the two theorists from the Institute of Nuclear Physics,, A. N. Grum-Grzhimailo and E. V. Gryzlova (the winner of the UNESCO 2012 L'Oreal award for "Women in Science"), was like the song goes: "paint on... later on, I will explain it all" (a reference to "The Painting Artists" by B. Okudzhava).

The task was to provide a theoretical interpretation for the photoeffect on the excited xenon atom, isolated from the influence of the nuclear magnetic moment. Nobody expected a quiet and peaceful life within the collective of 54 electrons, but the gradual improvement of the existing theoretical models finally led to success in describing the pure atomic photoelectric effect. This work, A. N. Grum-Grzhimailo says, is paving the way for a large class of studies with artificially disabled nuclear magnetic moments and for complicated atomic processes with isotope selection that we could previously not even think about.

### The paper is here: http://dx.doi.org/10.1103/PhysRevLett.111.243002


ELSE PRESS RELEASES FROM THIS DATE:

NOAA: Coastal ocean aquaculture can be environmentally sustainable

2013-12-19
NOAA: Coastal ocean aquaculture can be environmentally sustainable Little to no effects on coastal ocean environment seen with proper safeguards, planning Specific types of fish farming can be accomplished with minimal or no harm to the coastal ocean environment as long ...

Physical inactivity after cardiac surgery linked with substantially higher risk of depression

2013-12-19
Physical inactivity after cardiac surgery linked with substantially higher risk of depression Patients undergoing cardiac surgery should be assessed for depression and physical activity, say researchers in the Canadian Journal of Cardiology Philadelphia, PA, December ...

Survey reveals regulatory agencies viewed as unprepared for nanotechnology

2013-12-19
Survey reveals regulatory agencies viewed as unprepared for nanotechnology Three stakeholder groups agree that regulators are not adequately prepared to manage the risks posed by nanotechnology, according to a paper published in the peer-reviewed ...

New data compression method reduces big-data bottleneck; outperforms, enhances JPEG

2013-12-19
New data compression method reduces big-data bottleneck; outperforms, enhances JPEG New discovery is rooted in physics and the arts In creating an entirely new way to compress data, a team of researchers from the UCLA Henry Samueli School of Engineering ...

Data are lost to science at 'astonishing rate'

2013-12-19
Data are lost to science at 'astonishing rate' New evidence reported in the Cell Press journal Current Biology on December 19 confirms long-held fears about the fate of scientific data. Careful evaluation of more than 500 randomly selected studies found that the original data ...

New evidence that computers change the way we learn

2013-12-19
New evidence that computers change the way we learn People who use computers regularly are constantly mapping the movements of their hand and computer mouse to the cursor on the screen. Now, researchers reporting in the Cell Press journal Current Biology on December 19 have ...

New method to detect genetic defects in egg cells could double the success rate of IVF

2013-12-19
New method to detect genetic defects in egg cells could double the success rate of IVF Infertility affects up to 15 percent of couples around the world, and in vitro fertilization (IVF) is one way to treat this common condition. A study published by Cell Press December 19th ...

New gene responsible for cleft lip and palate syndrome identified

2013-12-19
New gene responsible for cleft lip and palate syndrome identified An international team led by researchers from Karolinska Institutet in Sweden has identified a new gene related to the Van der Woude syndrome, the most common syndrome with cleft lip and palate. The study ...

A new -- and reversible -- cause of aging

2013-12-19
A new -- and reversible -- cause of aging A naturally produced compound rewinds aspects of age-related demise in mice Researchers have discovered a cause of aging in mammals that may be reversible. The essence of this finding is a series of molecular ...

Scientific data lost at alarming rate

2013-12-19
Scientific data lost at alarming rate Eighty per cent of scientific data are lost within two decades, according to a new study that tracks the accessibility of data over time. The culprits? Old e-mail addresses and obsolete storage devices. "Publicly funded ...

LAST 30 PRESS RELEASES:

Process for dealing with sexual misconduct by doctors requires major reform

Severe pregnancy sickness raises risk of mental health conditions by over 50%

Early humans may have walked from Türkiye to mainland Europe, new groundbreaking research suggests

New study shows biochar’s electrical properties can influence rice field methane emissions

Guangdong faces largest chikungunya outbreak on record

Tirzepatide improves blood sugar control in children aged 10-17 years with type 2 diabetes inadequately controlled on existing therapies (SURPASS-PEDS trial)

An old drug, in a low dose, shown to be safe and effective in preventing progression of type 1 diabetes in children and young people (MELD-ATG trial)

Study reports potential effects of verapamil in slowing progression of type 1 diabetes

Fresh hope for type 1 diabetes as daily pill that slows onset confirms promise at 2-year follow-up

New estimates predict over 4 million missing people who would be alive in 2025 if not for inadequate type 1 diabetes care

So what should we call this – a grue jay?

Chicago Quantum Exchange-led coalition advances to final round in NSF Engine competition

Study identifies candidates for therapeutic targets in pediatric germ cell tumors

Media alert: The global burden of CVD

Study illuminates contributing factors to blood vessel leakage

What nations around the world can learn from Ukraine

Mixing tree species does not always make forests more drought-resilient

Public confidence in U.S. health agencies slides, fueled by declines among Democrats

“Quantum squeezing” a nanoscale particle for the first time

El Niño spurs extreme daily rain events despite drier monsoons in India

Two studies explore the genomic diversity of deadly mosquito vectors

Zebra finches categorize their vocal calls by meaning

Analysis challenges conventional wisdom about partisan support for US science funding

New model can accurately predict a forest’s future

‘Like talking on the telephone’: Quantum computing engineers get atoms chatting long distance

Genomic evolution of major malaria-transmitting mosquito species uncovered

Overcoming the barriers of hydrogen storage with a low-temperature hydrogen battery

Tuberculosis vulnerability of people with HIV: a viral protein implicated

Partnership with Kenya's Turkana community helps scientists discover genes involved in adaptation to desert living

Decoding the selfish gene, from evolutionary cheaters to disease control

[Press-News.org] Ways of the photoelectric effect; How physicists have learned how to select them