Tracking the ultrafast XUV optical properties of x-ray free-electron-laser heated matter with high-order harmonics
(1, 2)
,
(3, 2)
,
(4)
,
(5, 6)
,
(7, 8)
,
(8, 7)
,
(6)
,
(9)
,
(10)
,
(11)
,
(11)
,
(11)
,
(12)
,
(13)
,
(14)
,
(15)
,
(15)
,
(16)
,
(16)
,
(16)
,
(17)
,
(17)
,
(13)
,
(8, 7)
,
(4)
,
(18)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
P. Audebert
- Function : Author
- PersonId : 741794
- IdHAL : patrick-audebert
- ORCID : 0000-0002-1330-3946
Abstract
We present measurements of photon absorption by free electrons as a solid is transformed to plasma. A femtosecond x-ray free-electron laser is used to heat a solid, which separates the electron and ion heating time scales. The changes in absorption are measured with an independent probe pulse created through high-order-harmonic generation. We find an increase in electron temperature to have a relatively small impact on absorption, contrary to several predictions, whereas ion heating increases absorption. We compare the data to current theoretical and numerical approaches and find that a smoother electronic structure yields a better fit to the data, suggestive of a temperature-dependent electronic structure in warm dense matter.