Sub-Doppler spectroscopy of the PH radical: Hyperfine structure in the A [sup 3]Π state

Sub-Doppler spectra of the A?3?–X?3S-(0,0) and (1,0) bands of the PH radical have been recorded using an injection seeded single mode optical parametric oscillator in a supersonic jet expansion. Most of the rotational lines in these laser-induced fluorescence spectra exhibit clear splittings or asymmetry due to hyperfine structure. An analysis of this structure is presented in terms of the electronic structure and bonding of the molecule. Comparisons are drawn with the corresponding A?3? state of the NH radical, and some shortcomings in the accepted methods for interpretation are highlighted and discussed. © 2003 American Institute of Physics

INVESTIGATING STRUCTURE AND BONDING IN FREE RADICALS: MEASURING HYPERFINE STRUCTURE IN EXCITED ELECTRONIC STATES

Author Institution: School of Chemistry, University of Bristol; School of Chemical Sciences, University of East AngliaThe $A^{3}\Pi - X^{3}\Sigma^{-}$ electronic band system of the PH radical has been investigated at high resolution with a novel narrow bandwidth injection seeded optical parametric oscillator based on $\beta$-barium borate crystals. The OPO is pumped by the third harmonic from a single mode Nd:YAG laser and is seeded by an external cavity diode laser in the near infrared. This provides high power pulsed light simultaneously in the near infrared (idler) and the visible (signal) spectral regions at a resolution of ${\sim} 100$ MHz. The tuneable ultraviolet light required to probe the A - X electronic transition of the PH radical is generated by sum frequency mixing the signal wave with the second harmonic from the pump laser. The overall sub-Doppler resolution obtained in the ultraviolet allows hyperfine splittings due to the different possible orientations of the nuclear spin to be observed. Since the experimentally determinable hyperfine parameters contain expectation values over the co-ordinates of the valence electrons with unquenched spin or orbital angular momentum, they provide a direct route to unravelling the composition of the molecular wavefunction. Analysis of the observed hyperfine structure in the $A^{3}\Pi$ state of PH is presented in terms of the electronic structure of the molecule

An injection seeded narrow bandwidth pulsed optical parametric oscillator and its application to the investigation of hyperfine structure in the PF radical

We describe the construction of an all solid-state, narrow bandwidth, pulsed optical parametric oscillator (OPO) based on ß-barium borate nonlinear crystals. The OPO was injection seeded by an external cavity diode laser in the range 755–855 nm to generate high power narrow bandwidth tunable light in this range and simultaneously at 606–669 nm. The bandwidth of the visible light was ~130 MHz, and after frequency doubling or sum frequency mixing with the second harmonic of the pump Nd:YAG laser, sub-Doppler spectra with an overall resolution of 450 MHz were taken in the UV. The system is demonstrated by taking high-resolution spectra of the v' = 2–3 and 5–7 bands of the A?3?–X?3S-(v',0) progression and the v' = 4–v? = 0 band of the d?1?–a?1? transition in PF. These spectra show clear hyperfine structure, and an analysis of this structure is presented and interpreted in terms of the electronic structure of the molecule. As a prelude to this high-resolution study, the first ten members of the A–X band system and the first five members of the d–a band system were recorded at the moderate resolution provided by a pulsed dye laser

An ultra short pulse reconstruction software applied to the GEMINI high power laser system

The GRENOUILLE traces of Gemini pulses (15 J, 30 fs, PW, shot per 20 s) were acquired in the Gemini Target Area PetaWatt at the Central Laser Facility (CLF), Rutherford Appleton Laboratory (RAL). A comparison between the characterizations of the laser pulse parameters made using two different types of algorithms: Video Frog and GRenouille/FrOG (GROG), was made. The temporal and spectral parameters came out to be in great agreement for the two kinds of algorithms. In this experimental campaign it has been showed how GROG, the developed algorithm, works as well as VideoFrog algorithm with the PetaWatt pulse class