摘要:

AbstractThe collisionless infrared multiphoton excitation of small molecules, OCS, SO2, NO2and DN3is discussed. Despite the small absorbance of IR photons by these molecules, evidence for the population of highly excited vibronic levels below the dissociation threshold is obtained. Multiphoton dissociation is observed, as well. The average number of photons absorbed and dissociation yields depend predominately on the laser intensity. High order multiphoton processes couple the ground vibrational level with the quasicontinuum of excited levels below and above the dissociation threshold.

ISSN:0021-2148    

DOI:10.1002/ijch.198400031

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe multiphoton absorption of CO2laser 9 μm P(18), P(20) and P(34) lines by methanol has been studied for fluences from 10−3to ∼ 20 J/cm2, pulse widths of 6 and 60 ns FWHM and methanol pressures from 0.067 to 13.3 kPa. The absorption depends on laser fluence, laser line and gas pressure but not on laser beam intensity. For each line studied the results can be expressed as a function of fluence and the product of pressure with pulse width. Absorption by aQ‐branch transition (9P(34) pumping) shows a faster relaxation and a stronger absorption than R‐branch transitions (9P(18) and 9P(20) pumping). The results obtained here are compared to multiphoton absorption data for an HF laser pumping the OH stretch v

ISSN:0021-2148    

DOI:10.1002/ijch.198400032

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractSeveral experiments that examine the multiple‐photon absorption and dissociation and the post‐photolysis chemistry of tritium‐from‐deuterium isotope separation by 12 μ laser photolysis of chloroform are described. Results of recent experimental measurements of T/D selectivity in absorption and dissociation are reviewed. The fluence dependence of CTCl3IR photolysis is obtained from experiment and an energy‐averaged master equation model. Preliminary measurements of two‐frequency dissociation of CTCl3are presented. The pathways of the post‐photolysis chemistry are deduced from product formation in the 11 μ dissociation of neat CDCl3, and of the carbon‐isotope labelled reactan

ISSN:0021-2148    

DOI:10.1002/ijch.198400033

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractA relatively simple design for a hybrid CO2laser and electrooptic crystal switch is described, which can be used to produce pulses with fast (<10 ns) rise and fall times with constant power over their duration (50–1000 ns). Gaussian beam profiles allow separate and quantitative determination of both fluence (J cm−2) and intensity (W cm−2) dependences of processes induced by IR multiple photon absorption (MPA). Visible luminescence accompanying MPA of OsO4is shown to depend on intensity, and the dependences of MPA cross sections in SF6on fluence and intensity are derived from optoacoustic and long path absorption measure

ISSN:0021-2148    

DOI:10.1002/ijch.198400034

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractDetailed quantum‐dynamical calculations for the time‐evolution matrix of the IR multiphoton excitation of a small asymmetric molecule, including vibrational and rotational couplings, are presented. It is shown that rotationally and vibrationally specific multiphoton excitation is possible and gives inversions that are potentially useful for lasers in the IR and

ISSN:0021-2148    

DOI:10.1002/ijch.198400035

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe temperature jump relaxation method is applied to kinetic measurements in the gas phase. The system N2O4⇄2NO2is studied. Fast T‐jumps are induced by IR absorption from a TEA CO2laser. Temperature jumps of less than 1 K lead to readily detectable concentration changes which are monitored by UV absorption in a simple single shot experiment.krec(Ar) is found to be 1.05 × 1010cm3mol−1s−1atPAr= 1 bar andT= 258 K, in agreement with recent experimen

ISSN:0021-2148    

DOI:10.1002/ijch.198400036

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe multiphoton induced isomerization ofcis‐3,4‐dichlorocyclobutene (DCCB) was studied as a function of pressure. Three experiments indicated the existence of a nonthermal mechanism at neat pressures below 60 mtorr. These were: (i) the leveling off of the fractional yield of isomerization products at low pressures; (ii) the absence of dissociation products from 2‐iodo‐2‐methyl propane, which served as a chemical thermometer in the presence of a large excess of DCCB; and (iii) a break in the power‐law dependence of the optoacoustic signal produced by neat DCCB. The increased yield at higher DCCB pressures is believed to be due partly to a thermal reaction and partly to increased absorption caused by rotational or vibrational hole filling. Optoacoustic measurements also showed that at constant fluence the absorbed energy was greater for long, low intensity pulses, as might be expected for inhomogeneous excitation. However, the present experiments did not reveal an intensity dependence of the reaction yield. Addition of argon as a buffer gas monotonically decreased the yield, indicating that vibrational quenching more than offsets any hole‐fi

ISSN:0021-2148    

DOI:10.1002/ijch.198400037

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractThe infrared multiple absorption probabilities of the title molecules are measured at two frequency ranges: one for which the single photon absorption (SPA) cross section is large (range I), and another for which it is much smaller (range II). For SiF4, the high power absorption probability in range I is much smaller than the SPA cross section. Collisions significantly increase the average number of photons absorbed. In range II, the absorption cross section increases upon increasing the laser fluence. For anisole, the same fluence effect is qualitatively observed, but it is less pronounced in range I. For anisole pressure exceeding 0.1 torr collisions with argon do not change the average number of photons absorbed per molecule. The 10.2 μ absorption in SiF4is suggested to be initiated by a single photon hot band absorption, followed by absorption in the quasi‐continuum (QC). QC absorption cross sections are in the range of (5–20) × 10−21cm2for both SiF4and

ISSN:0021-2148    

DOI:10.1002/ijch.198400038

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractAn ion cyclotron resonance (ICR) spectrometer can be used to generate, trap, and detect gas phase ions which are irradiated with an infrared laser. Infrared multiple photon (IRMP) photochemistry can be conveniently studied under these conditions. Results of several recent studies are discussed.

ISSN:0021-2148    

DOI:10.1002/ijch.198400039

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY

摘要:

AbstractWe report upon the dynamics of the IR MPD of perfluoroalkyl iodides using visible laser induced multiphoton ionization of free iodine atoms in their ground state (2P3/2) as the probe technique. Stark shifting of an atomic MPI line by an intense infrared field was observed for the first time. The importance of an IR/visible double resonance dissociation through an excited electronic state was demonstrated and monitored through MPI of the excited spin‐orbit state (2P1/2) which is produced uniquely through this pathway. The consequences of the complications caused by these two effects for pump‐and‐probe experiments are discussed and methods to minimise their effect are sugg

ISSN:0021-2148    

DOI:10.1002/ijch.198400040

出版商:WILEY‐VCH Verlag    

年代:1984

数据来源: WILEY