Preparation and decay of alignment in N[sub 2] ([ital v]=1)

Journal Article · Thu Sep 15 04:00:00 EDT 1994 · Journal of Chemical Physics; (United States)

DOI:https://doi.org/10.1063/1.467457· OSTI ID:7256236

Sitz, G O ^[1]; Farrow, R L ^[2]

---

1. Physics Department, The University of Texas at Austin, Austin, Texas 78712 (United States)
2. Combustion Research Facility, Sandia National Laboratories, Livermore, California 94551 (United States)

We report measurements of the collisional decay of the angular momentum alignment for N[sub 2] ([ital v]=1) at 298 K. Stimulated Raman pumping of [ital S]-branch ([ital v]=1[l arrow]0) transitions is used to prepare a selected rotational state of N[sub 2] with an anisotropic spatial [bold J] distribution in the [ital v]=1 state. After allowing an appropriate time interval for collisions to occur, 2+2 resonance-enhanced multiphoton ionization is used (through the [ital a] [sup 1][Pi][sub [ital g]][l arrow][ital X] [sup 1][Sigma][sup +][sub [ital g]] transition) to detect the relative population and alignment of the pumped level and other levels to which rotational energy transfer has occurred. We have performed a series of measurements in which a selected even rotational level ([ital J][sub [ital i]]=0--14) is excited and the time-dependent level population and alignment are measured at several delay times. We find the decay of alignment to be no faster than the decay of the population of the pumped level, indicating that pure [ital m]-state changing collisions are slower that [ital J]-state changing collisions. We have also observed substantial alignment of molecules which have undergone a [ital J]-state changing collision. The alignment is this case is found to be inconsistent with a [Delta][ital m]=0 selection rule often used in models of rotational energy transfer rates.

• OSTI ID: 7256236
• Journal Information: Journal of Chemical Physics; (United States), Journal Name: Journal of Chemical Physics; (United States) Vol. 101:6; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
ANGULAR MOMENTUM
COLLISIONS
DECAY
ELEMENTS
EMISSION
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
IONIZATION
NITROGEN
NONMETALS
POPULATION INVERSION
ROTATIONAL STATES
SELECTION RULES
STIMULATED EMISSION
TIME DEPENDENCE