E. P. Snegirev

Ir absorption spectrum of CrO2Cl2 molecules for high-lying states of the vibrational quasi-continuum

Abstract A new approach to the spectroscopy of highly excited vibrational states of polyatomic molecules has been elaborated. The molecules of CrO 2 Cl 2 were prepared in states with a vibrational energy of the ground electronic term A 1 of ≈ 19000 cm −1 by means of internal conversion of electronic energy from the electronic state B 1 excited by laser radiation. The spectroscopy of the vibrationally excited molecules has been carried out in the region of the ν 6 and ν 1 bands with diode and CO 2 lasers. The fwhm of the obtained spectrum was ≈ 15 cm −1 . The intermode interaction in CrO 2 Cl 2 has been theoretically analyzed, and the calculated spectrum compared with that measured experimentally. The time evolution of the spectrum of vibrationally excited CrO 2 Cl 2 molecules has been studied. The average energy transferred per one collision with unexcited CrO 2 Cl 2 molecules was equal to 〈δ E 〉 ≈ 1200 cm −1 .

High-resolution spectroscopy of the ν2 Q branch of GeH4 with a computer-assisted, pulsed-diode laser spectrometer

Abstract The high-resolution absorption spectrum of the Q branch of the ν 2 band of the 74 GeH 4 molecule has been recorded. The accuracy of determination the line centers was 2 × 10 −3 −5 × 10 −4 cm −1 . The spectrum obtained has been interpreted. By simultaneously analyzing the states (0100, E ) and (0001, F 2 ) spectroscopic constants have been determined for these two states, as well as resonance constants of the type of X EF 2 Ω (K, Γ ) . The parameter values obtained reproduce the spectrum with an accuracy close to the experimental one.

Diode laser study of the ν1 and ν3 bands of the 120SnH4 molecule

Abstract The absorption spectrum of the SnH 4 molecule has been measured with Doppler limited resolution in the region 1903–1960 cm −1 by means of a tunable diode laser spectrometer. IR transitions of the Q and R branches of allowed ν 3 ( F 2 ) and “forbidden” ν 1 ( A 1 ) bands were observed. These two states were found to be strongly mixed by the rotational-vibrational interaction, and as a consequence the ν 1 band appears in absorption. Wavenumbers of transitions to the ν 1 , ν 3 energy levels with the quantum number of angular momentum J = 1–15 have been obtained with an accuracy of about 0.001 cm −1 . More than 230 transitions of the 120 SnH 4 isotopic species were used for simultaneous analysis of the ν 1 , ν 3 resonance states. In this way 21 spectroscopic parameters of the upper states have been determined using a model Hamiltonian which explicitly takes into account the resonance interaction. The parameters obtained reproduced the experimental spectrum with r.m.s. discrepancy of 0.002 cm −1 .

Study of the v 2 infrared band of GeH4: Q-branch

The results of recording of the diode-laser spectrum of GeH4, having a natural distribution of isotopes, within the range 932·4-937·5 cm-1 are presented. Taking into account the Coriolis interaction between (0100) and (0001) vibrational states, the rotational and centrifugal constants are obtained.

Stark effect on holes in the absorption spectra of phthalocyanine and the aluminum-phthalocyanine complex in polymer matrices

The effect of an external electric field on narrow spectral holes in S1←S0 absorption bands of molecules of free-base phthalocyanine and its complex with Al in polyvinyl butyral films at 4.2 K was studied. It was found that the average values of the change in the electric dipole moment due to phototransitions in the free-base phthalocyanine and its complex amount to 0.135 and 0.145 D, respectively. Both these values considerably exceed the relevant values for phthalocyanine complexes with Zn and Mg in the same matrix. Possible causes of the observed effects are discussed. Most probably, they are related to the differences in the structure of the central part of phthalocyanine-type molecules.

Diode laser stark spectroscopy on the persistent holes

Abstract The Stark effect on the hole-burning spectra of Zn- and Mg-phthalocyanine (Zn-, Mg-PhC) in polyvinylbutyral (PVB) films at 4.2 K have been measured using a tunable diode laser technique in the visible region. Simultaneously, with a linear Stark effect, a quadratic effect was also recorded. From comparison of the experimental data with the results of model calculations, the Stark parameters for both systems and a value of the internal electric field in polymer matrix were deduced. For Zn-PhC in PVB, we obtained average values of the induced dipole moment difference between ground and excited states: Δ μ ind =0.105 D; the polarizability tensor difference: Δ α =62 A 3 ; average local field value: E i =7×10 5 V cm −1 . For Mg-PhC in PVB: Δ μ ind =0.095 D, Δ α =50 A 3 and E i =6.5×10 5 V cm −1 .

Application of the Broad Hole Burning Technique for Studying Low-Temperature Photoreactions in Impurity Amorphous Bodies

A new experimental method is developed for measuring kinetics of low-temperature photoreactions—the broad hole burning technique, which eliminates the nonexponentiality of the hole burning kinetics caused by the inhomogeneous broadening. The method is successfully used to study the low-temperature photoreactions in various impurity amorphous systems. Examples of single-and two-exponential kinetics have been found, as well as kinetics with a moderate or large dispersion of the hole burning quantum efficiency. The results obtained show a good outlook for the broad hole burning technique for studying low-temperature photoreactions and illustrate the diversity of photoreactions occurring in specific chromophore-matrix pairs.

Improvement of sensitivity of diode laser spectrometer by optimal data filtering

In this work we applied optimal filtering for reduction of detection limit in a signal registered with the diode laser spectrometer. The noise of the spectrometer operating in pulsed mode was investigated and sources of noise were analyzed. The noise shows correlation within a single laser pulse and among different pulses. This fact of noise correlation was the reason of application of optimal filtering.