Experimental Rate Coefficients for Collisional Excitation of Lithiumlike Ions

Collisional excitation rates in N v, O VI, and Ne VIII have been derived from absolute line intensities emitted by these ions in a well-diagnosed plasma. The plasma was produced in a θ-pinch device, and several plasma conditions were investigated. The electron density and temperature were obtained as a function of radius and time from the spectrum of scattered laser light. The experimental results are compared with Bely's calculations using the Coulomb-Born approximation. Although the maximum error of the individual rate coefficients is a factor of 2, the standard deviation of the experimental values from the theoretical ones is less than 30% for excitation to the $n=2$ and $n=3$ levels and less than 40% for excitation to the $4s$ level. The rates to the $4p$ and $4d$ levels are on the average {~} 60% of the theoretical ones.