Rotating analyzer

The ellipsometer used in this study is described elsewhere(3). It consists of a Xenon light source, a monochromator, a polarizer, a sample holder, a rotating analyzer and a photomultiplier detector (Figure 1). An electrochemical cell with two windows is mounted at the center. The windows, being 120° apart, provide a 60° angle of incidence for the ellipsometer. A copper substrate and a platinum electrode function as anode and cathode respectively. Both are connected to a DC power supply. The system is automated with a personal computer to collect all experimental data during the deposition. Data analysis is carried out by a Fortran program run on a personal computer. 

Figure 1 A schematic diagram of the experimental set-up consisting of a rotating analyzer ellipsometer, an electrochemical cell with a copper substrate and a platinum electrode connected to a DC power supply. 

Because pyrrole has four C-H bonds, four C-H stretches are expected in two pairs, one pair of oscillators adjacent to the nitrogen and the other pair on the 3- and 4-positions. The origin of the fundamental C-H stretch vibrations in the gas phase has been intensively investigated <1995CPH(190)407>. The fundamental N-H stretch band has its origin at 3530.811343(82) cm and has been rotationally analyzed <1997CPH(220)311>. 

In order to use the Zeeman effect for background correction [306] several approaches can be applied (Fig. 87) [307]. A magnetic field around the primary source or around the atom reservoir can be provided, by which either the atomic emission lines or the absorption lines are subjected to Zeeman splitting. Use can be made of a constant transverse field and the absorption for the it- and the -components measured alternately with the aid of a polarizer and a rotating analyzer. However, an ac longitudinal field can be used and with the aid of a static polarizer only the cr-components are measured, once at zero and once at maximum field strength. 

The B2A"-X2A electronic transition of CaSH was rotationally analyzed in a pulsed molecular beam source by Scurlock et al. [113]. The a axis of this asymmetric rotor lies very close to the Ca—S bond and there is a large dipole moment of 5.36 D projected along it in the X2A state. 

A standard polarized-light microscope equipped with a Senarmont compensator, having magniflca tions up to 400X, and a rotatable analyzer with a graduated scale are used by the writer. All the obser vations are made with the use of the upper element of the substage condensing lens on the microscope. 

Errors when given are based on the statistics of Birge-Sponer plots. Rotationally analyzed as pure Hund s ease (a) transitions. 

Rotationally analyzed as transition from lower-state Hund s case (a) to upper state Hund s case (b). ) From [97Kaul]. 

Polarimeters on the other hand allow a quantitative measurement hy determining the stress-induced polarization change with a rotatable analyzer as described before. However, the measuring results obtained with manually operated polarimeters are strongly dependent on the operator and therefore subjective. In addition, colored glass is hard to measure since the intensity of the light source is often not sufficient for a reliable measurement. 

Fig. 2.15 Schematic diagram of a few possible configurations of automated ellipsometers. From the top to the bottom, a rotating analyzer ellipsometer (RAE), a rotating compensator ellipsometer (RCE), and a rotating analyzer with compensator ellipsometer (RACE)...

Figure 18-1. Geometry of standard null ellipsometer (a) and rotating analyzer ellipsometer (b). L, P, C, A, D and S represent the laser, polarizer, compensator, analyzer, detector and sample, respectively (after Jenkins, 1999).

To have fewer parts and to avoid mechanical transmission problems entirely, the rotating analyzer A and polarizer P were directly mounted onto the motor shafts, which were... 

D. E. Aspnes, Fourier transform detection system for rotating-analyzer ellipsometers. 

The Elliptic (or Brdce-Kohler) compensator is used for measuring the smallest retardations, with a maximum range of 20 or 50 nm and accuracy to 0.1 nm [57]. It has a birefringent plate that revolves in the horizontal plane. The Senar-mont compensator has an intermediate range, to 150 nm. It uses a X/4 plate and a rotating analyzer. For an explanation of how these work, see [19, 51, 52, 55]. 

---