Recombination Processes in Laser Produced Dense Cluster Plasma

Abstract

Various mechanisms of recombination of electrons with multiply charged atomic ions in atomic clusters irradiated by superintense femtosecond laser pulses are discussed. Some of the recombination mechanisms are shown to take a time considerably longer than the laser pulse duration and, hence, they can develop only in a homogeneous, fairly rarefied cluster plasma after pulse termination. All autoionization states of multiply charged ions in a dense cluster plasma have been found to be destroyed by the Holtsmark electric field. Therefore dielectric recombination does not take place in irradiated clusters during the laser pulse. Only collision recombination electron -ion -electron occurs effectively in dense cluster plasma due to high charge multiplicity of produced atomic ions inside the cluster.

Collisional recombination in strongly coupled plasmas

“…It is well studied for ideal plasmas [1,2]. It is also essential for strongly coupled plasmas (SCP) in a cluster [3][4][5], latent track [6][7][8] and ultracold [9][10][11] cases when multiple ionization is included (ions with charge Z > 1). Different approximations are used to analyze the influence of nonideality on the recombination [12][13][14][15][16][17][18][19][20].…”

Photoionization of clusters in intense few-cycle near infrared femtosecond pulses

“…Peltz et al 30 have pointed out that the main recombination channel to be considered in these dense nanoplasmas is three-body recombination (TBR) -the capture of an electron by an ion in the vicinity of a second electron. It should be noted here, following Krainov et al 31 and Peltz et al, 30 that many high-lying Rydberg states may not be available for recombination due to the local fields in the plasma. Thus, a cut-off in the maximum principal quantum number should necessarily be employed in estimations of recombination rates.…”

The role of collisional ionization in heavy ion acceleration by high intensity laser pulses

“…Recombination of ions can occur via free or bound electrons. Ion recombination due to collisions with bound electrons proceeds via charge exchange with neutral or partially ionized atoms of the target 25 , 26 . Free electron-ion recombination becomes important when bound electron-ion recombination drops sharply at high plasma ionization degrees 27 and consists of three processes: radiative recombination (RR), dielectronic recombination (DR), and three-body recombination (TBR) 14 (inverse process to electron CI).…”

“…Analysis shows that TBR occurs effectively in the dense plasma regions due to the high charge of ions. So, it occurs during the laser pulse, but, all auto-ionization states of the charged ions in a plasma are destroyed by the electric field, therefore, DR occurs in times considerably longer than the laser pulse duration in a rarefied plasma after pulse termination 25 . Moreover, the characteristic time of RR is in the order of a few hundred ps, which is very long compared to the fs laser pulse durations, hence it is less prominent than the DR and TBR mechanisms 25 .…”