- published: 01 May 2012
- views: 1199
Ultra-high vacuum (UHV) is the vacuum regime characterised by pressures lower than about 10−7pascal or 100 nanopascals (10−9mbar, ~10−9torr). UHV requires the use of unusual materials in construction and by heating the entire system to 180°C for several hours ("baking") to remove water and other trace gases which adsorb on the surfaces of the chamber. At these low pressures the mean free path of a gas molecule is approximately 40 km, so gas molecules will collide with the chamber walls many times before colliding with each other. Almost all interactions therefore take place on various surfaces in the chamber.
Materials which are not allowed due to high vapour pressure:
Technical limitations:
Ultra-high vacuum is necessary for many surface analytic techniques such as:
UHV is necessary for these applications to reduce surface contamination, by reducing the number of molecules reaching the sample over a given time period. At 0.1 mPa (10−6 Torr), it only takes 1 second to cover a surface with a contaminant, so much lower pressures are needed for long experiments.
If I could see you would you still give me
Just hold me tighter and love me maybe
You'll be my thunder, I don't want saving
You don't fool me, oh no you don't fool me
One look at you it's easy to see
oh no you don't fool me, oh babe you don't fool me
I'll play along, just give it to me
You build me up now, you pull me down
You make me come on yeah, keep me around
I'll want to move you, I surely could
You don't fool me, oh no you don't fool me,
one look at you, it's easy to see oh no
you don't fool me, oh babe you don't fool me,
I'll play along, just give it to me
---instrumental---
Just gotta have you, you drive me crazy, tell me you feel it, your honey give me ...
Here burns the fire, I feel your heat
You don't fool me, oh babe you don't fool me
One look at you, it's easy to see
Oh no you don't fool me, oh babe you don't fool me
I'll play along, just give it to me
Oh no you don't fool me, oh babe you don't fool me
One look at you girl, it's easy to see
Oh no you don't fool me, oh babe you don't fool me
I'll play along, just give it to me