Abstract
Liquid helium (LHe) at 4.2 K was electronically excited using a corona discharge for both negative and positive high voltages. The experiments were carried out for different pressures in the range from 0.1 to 10 MPa at constant temperature. The light emitted from the zone close to the tip was spectroscopically analyzed showing features from atoms and excimer helium. The shifts and widths of the observed lines and bands were found to depend on the applied hydrostatic pressure and on the tip polarity. Our analysis showed that classic pressure broadening theory cannot account for the observed widths and shifts rather than the presence of bubbles which surround single excited atoms and molecules. For positive tip polarities red shifted features distinct from pure He and He <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> * were observed and tentatively assigned to "red satellites".
Highlights
LIQUID helium is a fascinating substance with many peculiarities due to its highly quantum nature
Our analysis showed that classic pressure broadening theory cannot account for the observed widths and shifts rather than the presence of bubbles which surround single excited atoms and molecules
A particular feature of liquid helium is its intense luminescence in the visible and near infrared spectral range. This luminescence has been observed from superfluid 4He bombarded with energetic electrons [1,2,3], from liquid helium excited by a corona discharge [4,5,6,7,8] as well as from 4He droplets excited by monochromatic synchrotron radiation [9,10,11]
Summary
LIQUID helium is a fascinating substance with many peculiarities due to its highly quantum nature. The mechanisms involved in such a discharge in the liquid phase are complicated and involve electronic avalanches, energy transfer, formation of shock waves and bubbles, etc Another complication is that the particle density in corona discharge is not uniform [18]: the region close to the tip has a high excitation density and resembles in many respects a plasma. We further show that additional red-shifted spectral features exist that cannot be explained by rotational line intensity distributions of thermalized excimer molecules. These features depend on the polarity of the corona discharge giving rise to a provisional assignment to 'red satellites' side-bands. The microscopic origin of these red satellites is presently unknown
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IEEE Transactions on Dielectrics and Electrical Insulation
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
