Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Longest atomic state lifetime measured from spontaneous decay in UV

05.12.2002


Planetary nebula NGC3918, shown here, is a rare enough environment that atoms refrain from colliding long enough that scientists on Earth can study the spontaneous decay of atoms in very long-lived states.


The internal state of an atom can change by absorbing or emitting bits of light. In a warm gas or plasma the electrons are frequently shuttling back and forth from one state to another. Some of these states are longer lived than others, though, because of extenuating circumstances. For instance, many transitions from an excited state to the ground state occur in nanoseconds, but some can last for tens of seconds or longer. Measuring the true lifetime of the longer-lived of these transitions is difficult for the simple reason that ev en when a sample of atoms is dilute, an atom is being bumped so often that de-excitations come about before the state decays radiatively.

When even the best laboratory vacuum on Earth is still too crowded for making such delicate measurements, persistent scientists turn to outer space. Tomas Brage of Lund University (Lund, Sweden), Philip Judge of the High Altitude Observatory at NCAR (Boulder, CO), and Charles Proffitt of the Computer Science Corporation (Baltimore, MD) resort to viewing excited atoms in the planetary nebula NGC3 918 where, amid the wreckage of a dying star, there is enough energy to excite a toms but a density low enough (a few 1000 per cubic centimeter) that mutual pumping isn’t a problem (see image). Using the Hubble Space Telescope, the three scientists looked at the emissions of excited triply ionized nitrogen atoms and observed a lifetime of 2500 seconds for one particular hyperfine transition. Why is this state so robust?

Brage (tomas.brage@fysik.lu.se, 46-46-222-7724) says that angular momentum can be preserved in this transition only if, in addition to the electron emitting an ultraviolet photon, the nucleus itself flips over. Other than adding to basic knowledge about atomic physics , studies like these should provide spectroscopic information for studying the deaths of stars. (Brage et al., upcoming article in Physical Review Letters, probably 16 December; text at www.aip.org/physnews/select)

Phillip F. Schewe | AIP Bulletin
Further information:
http://www.aip.org/physnews/select

More articles from Physics and Astronomy:

nachricht Climate cycles may explain how running water carved Mars' surface features
02.12.2016 | Penn State

nachricht What do Netflix, Google and planetary systems have in common?
02.12.2016 | University of Toronto

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>