{"id":3654,"date":"2021-08-30T11:36:24","date_gmt":"2021-08-30T09:36:24","guid":{"rendered":"http:\/\/www.lac.universite-paris-saclay.fr\/?page_id=3654"},"modified":"2021-08-30T11:36:24","modified_gmt":"2021-08-30T09:36:24","slug":"the-k2-atlas","status":"publish","type":"page","link":"http:\/\/www.lac.universite-paris-saclay.fr\/?page_id=3654","title":{"rendered":"The K2 Atlas"},"content":{"rendered":"

\n
 
\n
<\/p>\n\n\n\n
\n
back
\nto the welcome page<\/a><\/center>\n<\/td>\n
\n
back to LAC<\/a>. homepage<\/center>\n<\/td>\n<\/tr>\n
\n
Direct
\naccess to the plates and tables<\/a><\/center>\n<\/td>\n<\/tr>\n<\/table>\n

<\/center><\/p>\n

\n
<\/h1>\n

\nI. Experimental conditions<\/font><\/h1>\n

 <\/p>\n

 
\n
 
\n
 
\n
 
\n
 
\n
 
\n
 <\/p>\n

The absorption spectrum
\nof the K2<\/sub> molecule in the 10487-12000 cm-1<\/sup> spectral
\nrange is presented in this Atlas. It is due to the transition between the
\n(A) 1<\/sup>Sigma<\/font>+<\/sup>u<\/sub>
\nand (X)1<\/sup>Sigma<\/font>+<\/sup>g<\/sub>
\nelectronic states. This spectral region is included in two previously published
\natlases [1,2].<\/p>\n

The present work was
\nperformed for two reasons:<\/p>\n

– the experimental
\nconditions proposed to the potential users are easiest to implement than
\nin the two previously cited references ;<\/div>\n
– the hyperfine structure
\naffecting the lines are of much fainter intensity than those in the I2<\/sub>
\ncase, leading to a better wavenumber determination.<\/div>\n
The used absorption
\ncell is represented in Fig. 1. It is a stainless steel pipe, 480 mm long
\nand with 63 mm external diameter. The active part is approximately the
\nlength of the heating oven i.e. 250 mm. The grid (250 mesh), made of stainless
\nsteel (type 304), is realized with a 40 m<\/font>m
\ndiameter (D) thread, the distance O between two consecutive threads being
\n61 m<\/font>m (Fig. 2). The grid is composed
\nof three layers of this wire gauze and extends after the cooling zone.
\nThe metal, evaporating in the central part, moves through the mesh due
\nto capillarity. The pressure of the metallic vapour is balanced by an inert
\ngas, argon, preventing from potassium condensation on the windows [3].
\nThe heat pipe is inserted in a White type cell, ruled for four passes (Fig.
\n1), and giving a one meter absorption length [4].<\/div>\n
The K2<\/sub>
\nabsorption spectrum was recorded under the following source conditions
\n:<\/div>\n
argon pressure 6 mbarr (610 P) ; temperature
\n550 K. The continuous background spectrum is provided by a 250 W halogen
\ntype lamp (tungsten wire), the electrical power being limited to 90 W during
\nthe experiment. The Fourier transform spectrometer used for the spectrum
\nrecording is described in [5].<\/div>\n

<\/p>\n

<\/center><\/p>\n

\nII. Presentation of Plates and Tables<\/h2>\n
Each page of the atlas, noted Page_001,
\n002,…<\/b>reproduce equally spaced ranges of the spectrum. A small overlapping
\nspectral range exists between successive plates. The vertical scale, indicating
\nthe absorption of each line profile, is given in arbitrary units but the
\ncontinuous background is normalized to unity for each plate. The estimated
\nlocal noise [6] is visualized at right of the vertical axis by a line portion
\nlimited by two opposed triangles. The wavenumber scale is equal to 0.5
\ncm-1<\/sup>\/cm when the distance between abcissae ticks is 2 cm. Each
\nreference line is marked by a vertical tick, located in the upper part
\nof the spectrum. These ticks are numbered each 5 value, the corresponding
\nticks being longer. A spectral line is retained as a reference one if the
\ntwo criteria are fullfiled :<\/div>\n