Ruby laser, flash photolysis using

The complex formation of bilirubin with human serum albumin was investigated by Sinclair et al. 72) using 347 nm ruby laser flash photolysis technique. A high bilirubin level is found in new bom babies who suffer from jaundice (neonatal hyperbilirubinemia)73). Phototherapy has been found to be suitable for lowering the bilirubin level. In order to understand the mechanism of the phototherapy, investigation into the photophysics of bilirubin is essential. It is strongly bound to human serum albumin, lipids and cell membranes. 

Absorption spectra were recorded in a Perkin-Elmer spectrophotometer, and fluorescence spectra were recorded on a Perkin-Elmer Ul+B spectrofluorimeter. Flash photolysis studies were carried out using an excimer laser, X excitation = 3080A°, a ruby laser, X excitation = 3 71A°, or a nitrogen laser, X excitation = 3391A°. The system has been described previously. 

An ideal monochromatic source is the laser or uvaser. There is little or no published work on continuous photolysis using these sources although we must be on the threshold of this happening. Porter and Steinfeld have flash-photolysed phthalocyanine in the vapour phase using a Q-switched ruby laser. This emits at 6943A, and 2-3 J are dissipated in 20 psec. Photolysis occurs because of a two-photon process. 

An intense short pulse of UV or visible radiation is used to electronically excite the sample, and the subsequent absorption changes are probed spectrophotomet-rically. The technique was first introduced by Norrish and Porter in 1949 [18] and at this time gas-filled discharge lamps were used, limiting the time resolution, which is principally governed by the duration of the excitation pulse, to microseconds. This is now usually termed conventional flash photolysis. However, with the development of laser pulsed techniques in place of flash excitation, the time resolution has been progressively reduced to subpicosecond, particularly with the use of mode-locked solid state lasers. Much current work utilises nanosecond time resolution with pulsed lasers such as ruby, neodymium and excimer lasers. 

---